I moved to Giff Gaff for my iPhone in April 2012 and wish I'd done it sooner. Just click the banner and 'hey presto', free SIM from me :-)
As soon as you activate it, you get £5 free credit and so do I - brill.
You can even keep your old number - the porting process took only 1-2 days for me!
So many 'Goodybags' of things to choose from - click on the banner for more info:
