Thankfully, that's all about to change in February, as O2 has brought its iPhone tariffs in line with regular O2 deals. For those on the cheapest £35-per-month package (such as yours truly), minutes get tripled to 600 and texts to 500 per month, and the £45-per-month package gets bumped to 1200 minutes and 500 texts (previously costing £55). O2 has decided to remove the £55 option of the past, and will reduce their future bills to £45, or allow them to move to the £75, 3,000 minute / 500 SMS package. If you have your iPhone on O2, you'll want to check out this page for the complete low-down.
[Via twitter / Macworld and thanks to all those who sent this in!]