Deano, I'm in a good mood this week because of all the nice things people have said about us on here, so hopefully this will help you.
Ste is right you can get them from CPW for a tenner, but you have to buy a topup as well, which as you're on contract would be a bit pointless. Cheapest phone around at the moment (afaik) is the LG GB102 at £8.97 from Tesco, now it's on T-Mobile but if you bring it in to my place I'll unlock it for you for FREE so you can use your Orange sim in it.
The phone isn't the best on the planet, but for under a tenner what do you want ?
Just take it in to the shop, if I'm there I'll do it for you straightaway, if I'm not then I'll do it as soon as I get in, I'll leave a note for them in the morning that there is a freebie coming in.
332-336 Old Chester Road
0151 644 0880