AGED just 26, Rachel Maclean may well be the best Scottish filmmaker you've never heard of.

It isn't unreasonable, either, to apply that same title to her work as an artist, performer, maker of photographic images and costume designer. She's certainly the only person I've encountered who's prepared to dress as the Artful Dodger in a costume made from a cut-up Rangers top and a ginger wig, apply make-up to give the illusion of rotten teeth and then lip-synch to a clip of a Britain's Got Talent contestant singing Consider Yourself. While someone films her.

The wig is gone and the teeth are back to normal when we meet in her studio, a spare room of the flat in Glasgow's East End she shares with her boyfriend. But the costume is hanging up behind her, just one of several that feature in her latest video work, Please Sir... Described by her as Oliver Twist meets The Prince And The Pauper, it's showing at the city's CCA this month as part of the National Galleries of Scotland's country-wide Generation project, a survey of 25 years of contemporary art in Scotland. Maclean is one of its rising stars.

In fact, "studio" doesn't quite cut it as a description of this room. It's a massive walk-in wardrobe crammed with the strange and fabulous garments which have featured in previous Maclean productions such as A Whole New World, made with the £10,000 she won as recipient of the 2013 Margaret Tait Award, and The Lion And The Unicorn, a commission from Edinburgh Printmakers and exhibited there last year as part of the Edinburgh Art Festival.

She talks me through a few of them, pointing out which films they feature in and how they were sourced. Wonderful thing, eBay. "There's one with boobs as well," she says, riffling through a packed clothes rail and pulling out a dress I can't believe I haven't already spotted. Attached to it are a pair of fake breasts, painted a peach colour. I can also see pith helmets - Carry On Up The Khyber re-imagined by Alexander McQueen, perhaps - and a gaudy unicorn's head. If Barbie ever took acid, this is what Ken would be carrying under his arm in her nightmarish flashbacks.

Maclean's 2013 film Germ, a three-minute commission for Channel 4's Random Acts slot, parodied television advertising. In the colour-saturated Lolcats, meanwhile, we see her dressed as a cat and lip-synching to an interview in which Katy Perry discusses Britney Spears's amazing white teeth. But the central thrust of much of her work deals with issues closer to home - cultural and national identity, and the historical schisms and alliances that inform how we feel about those things. It's an interest shared with older Scottish artists such as Roddy Buchanan, Ross Sinclair and Calum Colvin, and it was born of her time studying at Edinburgh College of Art.

"A lot of it came from walking up and down the Royal Mile," she says. "I was quite keen on the kitsch aspect of that sort of thing, and the touristic, fantasy world that's been created that sits on top of the reality of Scottish life. I looked at that through the lens of Braveheart, this idea of playing with identity. I had a lot of characters with Saltires on their faces."

When Edinburgh Printmakers asked her to make a work to be shown at historic Traquair House in the Borders in 2012, she came up with The Lion And The Unicorn, a meditation on the Union. "It wasn't too long after the SNP victory. There wasn't a date then for the referendum but it looked like it was going to happen so I felt it would be interesting to take ideas I'd been thinking about purely in terms of identity, and make it slightly more politicised."

In that film, a Union Jack cake is cut into pieces as Maclean, dressed in an 18th-century-style dress made from the Union flag, lip-synchs to a speech by the Queen concerning the Jubilee. In I Heart Scotland, an exhibition of large-scale images which accompanied The Lion And The Unicorn, the same figure can be seen in a glossy photo-montage titled The Baptism Of Clyde. It also includes praying figures wearing dresses made from Celtic tops. In another image, St George And The Monster, a golf club-wielding man mounted on a unicorn and with an English flag painted on his face chases a woman wearing a dress made from a Rangers top. In the foreground, the decapitated head of a CU Jimmy hat-wearing Nessie lies on the ground, tongue lolling.

Make of that what you will. But it's safe to say that Maclean enjoys the comedic, the sinister, the absurd and the grotesque, and there's an unsettling creepiness to both her still images and her films which undercuts the Teletubby cheerfulness and surface sheen. A Whole New World, for instance, takes all this and applies it to Britain's role as a former imperial and colonial power, and both that film and The Lion And The Unicorn will be showing alongside Please Sir... at the CCA in an exhibition whose collective title is Happy & Glorious. In case you need a pointer, that's the line from the British national anthem before the "long to reign over us" bit.

Is the title ironic? Antagonistic? A veiled entreaty to vote no in the independence referendum? Maclean won't say where she's putting her cross on September 18. "I don't want my work to say either yes or no," she says. "I'll be voting one way, but I don't want my work to be about that."

Neither is she concerned about cutting up and appropriating Rangers and Celtic tops to make statements, albeit heavily codified ones, about issues of nationality, religion and self-representation. "I don't think there's been any comeback," she says, "unless galleries have had some and haven't told me." She doesn't care for football nor support either team.

So what conclusions has she come to about national identity? "I think there's a sense of national identity being something that's genuinely important to people - something that, if it was taken away, you might feel you were losing an important part of who you are," she says. "But at the same time there's something absurd about it, about the outward shows of identity and the symbols and signifiers of national identity and nationalism that I wanted to make fun of at the same time as buying into. With national identity I think you can be simultaneously sentimental and critical."

What's different about Please Sir... is that this time Maclean is throwing class into the mix too. As well as clips of that Britain's Got Talent contestant - 12-year-old Callum Francis, if you can remember the 2009 auditions - we see Maclean mouthing words spoken by judges Piers Morgan and Amanda Holden while the story arc takes its cue from The Prince And The Pauper. To that end, Maclean has DVDs of the film versions piled on her desk. Yes, even the Raquel Welch one, which perhaps explains the dress with the peach-coloured boobs.

Please Sir... is "a specifically British look at representations of class, particularly in television and media," Maclean says. In its gallery format it's going to be shown on two screens, "one at either end of the room, as if you have a character talking on one screen and looking out and talking to the character on the other. I was quite keen that it's almost like a physical space, so the characters can walk from one screen to another and back. Also there's a sense of a simplistic duality - the idea of these characters swapping places and an idea of mistaken identity that I'm quite keen on."

Technically, Maclean's films work like this: she makes costumes and designs sets, constructs a narrative using what she calls "found" audio (anything from a David Cameron speech to lines from TV shows) then films herself acting and lip-synching against a green background. This allows her to then place myriad versions of herself against other backgrounds which she creates on her computer using digital imagery and copyright-free stock photography. Then she edits it all together with software such as Final Cut and After Effects.

Getting it right is fiendishly complicated. To prove the point she shows me her storyboard for Please Sir..., a folder containing page after page of drawings and annotations. "In terms of shots with multiple characters you have to set up eyelines for each character, so you're looking at a bit of a paper on a board and imagining it," she says.

As her films grow in scale and ambition they also require her to collaborate with an ever-increasing number of sound designers, lighting engineers, directors and cinematographers. "What's been nice about working in bigger studios is that I've been working with more people. I've been working a lot with [cinematographers] Ian Forbes and David Liddell. They have a really creative way of using light."

What's also notable about the work, beyond its wit, its zeitgeisty themes, its nagging weirdness and barbed charm, is that it's Maclean and only Maclean who features in it. In that sense she bears comparison with American artist Cindy Sherman, the conceptual photographer who takes portraits of herself in a range of guises.

"I think what I like about just using myself is this idea of there only being one person split into lots of different identities," she explains. "It heightens the absurdity and the fantasy to the extent that these are hermetically sealed worlds you can never enter. When I started off, I also liked the idea of taking myself and exploring multiple female identities too.

"And I quite like a lot of sketch shows and British comedies that have one person playing multiple people, things like The Fast Show and The League Of Gentlemen. I like the sense of it heightening the grotesque. And I've always liked dressing up. I've always liked the idea of imitation and voice imitation. That's part of what dressing up is."

Born in Edinburgh, raised in Dollar and educated at Dollar Academy, where her parents taught art, Maclean studied drawing and painting at Edinburgh College of Art and graduated in 2009. She also spent time as an exchange student in Boston, which introduced her to New York's video art scene and the work of American artists such as Ryan Trecartin. "A lot of it was referencing pop culture. It was in-your-face and colourful and I was excited by that idea," she says.

Returning to Edinburgh and being introduced to green-screen technology on one of her study modules, she began to experiment. She was already drawn to collage to create what she calls "fantasy worlds" and found she could apply the same principles to video art and still photographic images.

"The limitation I'd seen with the moving image before was that you can't quite have the same level of control over the world. But with green screen it was exciting because you can almost recreate the space that you would get in a painting or in a collage. My degree show was a mixture of painting and video but the more I went on the more I realised that what I could do in painting I could do in a more interesting way using photographic images."

As a teenager, Maclean discovered the work of Calum Colvin and studied the paintings of the Renaissance, and as a student she looked at the work of Georgian satirists William Hogarth and Thomas Rowlandson. In the first she found Scotland's pre-eminent analyst of national identity, in the second classic templates she could apply to her own figurative compositions, and in the third a means of approaching the sort of art she wanted to make.

But in turning to film to do it, she was also returning to a childhood hobby. "I did a lot of home videos when I was wee," she laughs. "I was quite into filming stuff - just mucking about with friends and making horror films with stories we made up as we went along. But I had really good fun with that."

So does she have plans to take her themes and her world view - as well as her continuing desire to have fun - into the mainstream and direct a feature film? She wouldn't be the first to make the journey. Video artist and 1999 Turner Prize winner Steve McQueen has gone from art gallery to multiplex and won an Oscar.

The answer is a maybe. "The next work I make is going to be scripted and I will try to work with actors," she says. "It's something I've wanted to try for a while. I feel I'd like to try something else. It might not work but I can see the limitations of me being the only actor. I could do things in a different way ... if something's been in my head for a while I should probably give it a shot."

She's probably right, so watch this space - and if it has a green screen attached, the results could be spectacular.

Happy & Glorious is at the CCA, Glasgow from May 31 until July 13 as part of Generation 2014, www.rachelmaclean.com, www.cca-glasgow.com