(25k+ hopefully 30k)
Unless you work in London I think your find thats very difficult to achieve. Obviously if you do live in London, then you have to pay for extra living expenses, or the commute if your outside.
What exactly are you trying to get into in Computing? I suggest you decide what you want to do and build a portfolio of sort or get some experience in that area. Eg, you want to be a Java Programmer, well then play around with Java more. E-Commerce? Get playing with MySQL, Networking - SQL Server etc, you get my idea