As someone has mentioned National Savings, you might think about bunging some or even all of it into Premium Bonds. At least as safe as a government-backed bank account, and any winnings are tax-free.
If you put a lot in, chances are you will get several small prizes (minimum is now £25) over the year, roughly in line with the notional (miserly) rate of interest they pay. But then most savings interest is miserly at the moment, and in theory, you have the chance of winning a bigger prize.
Bear in mind that it will take probably about a week to get your money out when the time comes that you need to withdraw it all; maybe up to two weeks. You can apply to buy them online, but to withdraw them, you need to get a form from the post office (or maybe NSandI will send you one).
When you start investing with them, you can sign a form to say that you want any winnings you get re-invested (up to the maximum holding of £30,000). Failing that, they would send you the equivalent of a cheque for any winnings. If you win a million, then I believe they bring it to you personally (along with investment "advisors" I shouldn't wonder...).
I have never won more than £50 from a single bond, although I have had 2x£50 in one month I think, but my holding has never been more than a few thousand. I get the impression that the large prizes tend to be won by those with big holdings.
