Put it in an ISA.
Not only does it gain a heck of a lot of interest, it's also likely to make you think before you take it out.
The limit is £3000 per tax year, and whever you make a withdrawal you can't put that money back in. So say you put in £3000 (I wish) If you decide to take out £1000, that money can't go back in, so it brings your limit to £2000.
It should make you think before frivolous spending.
Double your monthly payment on bills that are regular living expenses, i.e. phone, cable, internet, insurance, utilities. When you get ahead on some of these bills, you can relax a little if you have a "tight" income month. Don't double your mortgage payment, though, because that is usually considered an "extra" payment, not "next month's" payment.
Set up a standing order to a savings account to go out the day you get paid. Don't make my mistake though and send it to a savings account that you can access via your internet banking and transfer the money at a click of a button!! Open one of the savings accounts that you can't access on the internet and the more withdrawls you make the less interest you earn.
Why not create a savings account with another bank/building society to the one that your current account is with. Using internet banking is also helpful, as you can transfer money between companies, but not instantly, such as if you see a great pair of shoes that you can't afford! I've found that this has helped me think a bit more about purchases and which I can afford. Hopefully it will be helpful for you too!