At the moment I have 3 iPhone Simplicity contracts with O2 giving 600 minutes, 1200 texts, and unlimited Internet and wi-fi for £60 per month (£20 each). O2 have been very unhelpful about supplying replacement microsims and tell me that the data will be capped from October onwards.
Vodafone will do me 600 minutes, 3000 texts, 1GB of data, and 1GB of BT Openzone on each of three 12 month sim only plans for a total of £50 per month.
I'm fed up with O2 coverage so this is a great deal for me and my family even if we will no longer have visual voicemail.