HANGING around Glasgow Central Station at 10pm on a freezing Monday night is a surreal experience made all the more discomfiting by the guard repeatedly telling you the sleeper train to London you're anxious to board isn't ready yet.

There are only so many times you can wander round M&S Simply Food before you start looking suspicious. So finally being allowed entry to the warm, bright and busy Caledonian Sleeper, and being shown to my very own little berth, was a magical experience akin to what you imagine it must be like to travel on the Hogwart's Express.

That, unfortunately, is where the comparisons end. On surveying my miniature cabin, I had to double-check it was actually first class. "Oh, yes, madam, the only thing that makes this first class is that you have the cabin to yourself," replied carriage host Liam.

Plus you get a fresh fruit salad with your instant breakfast coffee. Standard-class passengers travelling alone have to share the constricted space with a stranger.

The yellowed plastic, navy livery and scuffed sink reminded me of travelling on the sleeper in the early 1980s when I lived in London. I was astonished to discover the rolling stock has not changed one bit. There are no electrical sockets in the cabins, meaning mobile phones or laptops can't be charged overnight. Neither are there showers on board and you have to pad down the corridor to the public toilet.

ScotRail has an agreement with Virgin that, on arriving at Euston, customers can use its first-class lounge to shower, drink coffee and read newspapers. On the morning I arrived last month, the showers were running cold.

On the plus side, the on-board lounge is lovely. Its leather sofas, deep-pile carpets, low lighting and convivial host are obviously attractive to travellers. On the night I travelled it was pleasantly buzzing.

The service leaves Glasgow at 11.40pm and arrives in London at 6.40am.

Richard McPike, who works with the Prince's Trust, was travelling from his home in Kilmarnock to attend a meeting in central London the next morning.

"The sleeper is so convenient," he said. "I don't mind flying, but it's too much of a red-eye. You've got the car park, check-in, security and all the other things before you get on the plane.

"The train is a no-brainer for me. It's much better than getting up at stupid o'clock to catch a plane."

Tom Greatrex, Labour MP for Rutherglen and Hamilton, was also using the sleeper. Asked what he would do if it was axed, he said: "It would be less convenient, because to get to a Westminster meeting at 9am would be well-nigh impossible, even on the red-eye flight from Glasgow. The first flight to London City gets in at 8.20am, but that's too tight.

"I have two-year-old twins and we live in Cambuslang.

"If I want to catch the last flight from Glasgow in the evening, I need to be at the airport for 7.15pm, which means leaving the house by 6.45pm – bang in the middle of bathtime.

"I wouldn't use it at all if the service were rerouted to Edinburgh. I'd end up feeling exhausted. It would limit my duties as an MP."

Angus MacNeil, SNP MP for the Western Isles, caught the Caledonian Sleeper by the skin of his teeth – after two flights from Stornoway had been cancelled due to icy weather – and got the last berth available.

"The London to Glasgow service is more important for me," he said. "If I work late in the evening at Westminster, I catch the train, then get the early flight to my constituency.

"In the UK we're lucky and unlucky. The Victorians built what we've got but no-one has built on that."

Brian Morton, an employment relations manager for the Royal College of Nursing, travels once a fortnight to London for meetings. He said: "I definitely support this service. I live in Ayrshire, so if it were to be cut to Edinburgh only, I wouldn't use it."

On my journey back from London to Inverness, the waiter laments the old kitchens with proper gas grills, and a "really posh" menu, which disappeared when railways were privatised.

"Now we have two microwave ovens and a limited menu," he said. My haggis, neeps and tatties (£5.95) are okay. Others opt for chicken curry with basmati rice (£4.70). A glass of red wine is £4.95.

Malcolm and Jane Steven, Linda Stuart and Maggie Adam are all retired healthcare professionals travelling from Euston to Nairn after a culture break. Ms Adam told me: "We desperately need the Inverness service. You have to get up at 5am to catch the 6.50am Flybe flight and you don't get into London until 10.30.

"The sleeper is convivial and very relaxing."

Waking at 6.30am to find Blair Atholl blanketed in snow, with the sunlight dawning over a magical Highland landscape, I see what she means.

We're bang on time and even the instant coffee somehow tastes good. The Caledonian Sleeper may not be perfect but it can still cast quite a spell.