GiffGaff (O2 child company) have reduced their bundle deals by half price through July but more importantly have stated that there will be free internet on all their SIMs until the 1st of October 2010.
Their bundles can be found here. 100 minutes/100 texts is now £5 per month or 8p min/4p text without the bundles. Free data on both.
I've been with them about a month or so and it's fantastic. GG and Virgin were the only ones I could find that were doing pay as you go direct debit. No more stupid top up hassle.
Help is provided through very active forums and the means to reward helpful posters. Speaking of which, if you sign up I might be able to earn a few points as a referrer [Coastal].