Most of my investments in a stocks and shares ISA average a return of 10 percent per year (in total they have increased by 300 percent over the past 5 years). No debt is that expensive in the UK
Thats incredible, are you money minded or you do have a person to help you? ie do you manage and keep on top of it yourself.
It's perfectly possible, and I get the same sort of returns. There are very reputable investment companies/websites where you can create an online portfolio, sheltered in an ISA, using their best advice and recommendations for managed funds, etc.
Essentially, you are buying into their advice and in turn that gives you the expertise of the individual fund managers, who then invest in stocks, shares, gilts, whatever, in the UK or overseas. It's nothing like managing a portfolio of individual stocks and shares for yourself.
It's medium to long term investment, so once you've made the initial investment, it's just a matter of checking back in every 3 - 6 months to make sure you didn't buy a turkey somewhere down the line. You have to hold your nerve when markets fall, but the trend is generally upward and a lot better than 1% interest on a cash savings account!