Say you spend £2 per week - why not save up the money over a year - in an old sock or whatever - and reward yourself? - All you need to do is to buy the bonds, online or in a Post Office at a minimum purchase of £25 and these will be entered into the monthly draw which carries a range of smaller prizes including a million pounds.
For Christians who object on moral grounds - you are not even gambling! You never lose your stake - and you can cash in whenever you please.
The only downside, of course, is that your investment will gradually erode due to inflation.