It's not a case of either a savings account or stocks. There is nothing wrong with splitting the sum between savings accounts with handy banks or building societies and putting the rest in a selection of unit trusts or investment trusts. Some funds have higher risk than others - small companies or emerging markets are generally regarded as high risk while blue chip UK stocks are low risk. The best way to see what could happen to your money is to look at a chart of some stock indeces. The footse index of the 100 largest UK companies is currently about 3% lower than it was 3 months ago, 9% lower than 6 months ago, 3% higher than 1 year ago, 11% higher than 2 years ago, and 60% higher than 5 years ago. If you can put up with those sort of fluctuations, then you should certainly consider investing part of your money into a fund investing in large UK companies. You should not put the whole amount into one savings account or one investment fund. Beyond that advice, you need to make your own decisions about how much risk you want to take and who you are willing to trust to handle the money - it is worth restricting your stock investments to larger unit trusts and investment trusts though and there are plenty of those to choose from.
One investment I would recommend is spending a few pounds at your newsagents on next week's Invertors Chronicle.