Turning photos into posters for a surpprise party. Where?

[wheresclaire]

I have about 20 photos I need to blow up (only about A4) for a party. Where can I get something like this done in norwich? Would it be a printers, like Colmans in Sprowston? Or would ASDA or Tescos be able to do it? Any ideas how much it will cost me?

Try www.photobox.com, upload your pictures and you can choose how big (poster size)