The FTSE-100 may have hit new highs but half of investors still plan to increase their stock market exposure in the coming months, according to a survey of investment trust shareholders.

The ideal way to do that will be to take advantage of the annual Isa allowance, at £15,000 for this tax year for the first time, rising to £15,240 from April 6 for the next tax year.

Only 8per cent of Isa holders take up the full limit, and although the tax advantages are much vaunted they may in practice make little difference to any investor who is not in the higher tax bracket. For basic rate taxpayers, dividends are already taxed and there is no more to pay, while each individual has a capital gains tax allowance to set against profits made from selling investments, currently at £11,000 a year.

But among those still looking to invest in the months ahead, the predominant reason given was the continuing rock-bottom rates on savings.

This week marked the sixth anniversary for historically low interest rates of 0.5per cent. A Blackrock survey has found that Brits hold 68per cent of their savings and investments in cash, whilst admitting that ideally it should be only half that proportion. Blackrock's Alex Hoctor-Duncan says: "Even those who chased the best bank and Isa rates over the last six years have made a loss when inflation is taken into account, with annualised returns of minus 1.7per cent. As the end of the tax year approaches, savers should think about using their Isa allowance to take steps out of cash and seek more effective ways in which their savings can provide an income to make their money work harder for them."

Using an investment platform to do it yourself has become less of a minefield now that charges and fees are more transparent. The cost of any fund and the charge for using the service should now be clear and easy to compare, while providers are stepping up the level of information and guidance they offer and improving the user experience.

The new breed of sites such as Rplan, Nutmeg and Strawberry Invest offer pre-selected portfolios for different risk levels.

Stuart Dyer at Rplan said: "Investors everywhere have a bias towards domestic investments, usually because they feel it is what they know. Unfortunately, it is not a great idea for any investors to be significantly overweight to any particular sector. Our own research last year found that nearly half of UK retail investors had over half of their portfolios in UK equities and bonds and that is alarming: it is imperative that they have a balanced portfolio to reduce volatility and risk."

But for those prepared to make their own choices the advice is to do your homework and don't place too much reliance on 'recommended' funds on broker lists. According to Trustnet Direct, which offers a performance screening tool for every fund in the market, funds which are promoted with 'discounts' on certain sites could be the ones managers find harder to sell. Managing director John Blowers told The Herald: "I heard one fund manager say 'we don't need to discount our good funds, so we give them a crap fund'."

But the favoured picks of the big platforms do offer a starting-point for investors to get thinking about the markets, and their strategy.

Popular platforms have traditionally ignored investment trusts, but Tilney Bestinvest offers access and suggestions. Managing director Jason Hollands says: "While less numerous than their open-ended cousins, and often ignored by broker buy-lists, investment trusts can represent a superior choice, especially when it comes to accessing illiquid asset classes or volatile markets."

Yesterday Alliance Trust announced it would increase its dividend for the 48th consecutive year, on a par with the Bankers and City of London trusts and one of many to lift payouts for more than 40 years in a row.

The Association of Investment Companies says almost half of conventional investment companies currently offer a dividend yield (return) of 3per cent or more.

It has also found, in research with Morningstar, that savvier private investors are switched on to the sector. Some 46per cent of respondents said investment companies were likely to deliver

the best long-term returns in a pension scheme over 20 years, with 22per cent saying open-ended funds, 17per cent ETFs and 15per cent saying no difference.

But the growing popularity of the trusts with the highest yields, such as Edinburgh-run Murray International, has led to 50per cent of higher-yielding trusts trading at a premium to their asset value. "In other words, the shares cost more than the value of the underlying assets," the AIC notes, which may make them less attractive to some investors.

Mr Hollands highlights five trusts for different investment profiles that merit attention. Keystone, managed by Mark Barnett, as a core defensive holding largely invested in UK equities; Baillie Gifford's Scottish Mortgage, run by James Anderson, with only 7per cent in the UK and 21per cent in China for a racier pick, trading at a modest premium; Value & Income for a UK-focused trust offering a 3.8per cent yield and trading at a substantial discount; Jupiter European Opportunities, which can gear up (borrow) substantially to boost returns in a rising market; and JPMorgan Emerging Markets, which has 22per cent in India, and trades at a wide discount.

Investment plans offer a low cost route into long-term growth, such as Scottish Investment Trust's Isa which charges 0.6per cent but caps the charge at £36 whatever the amount invested.