o2 does seem a poor network choice, as i found their 3g very flaky last time i used a phone on o2 about 6 months ago. Sounds like they were most willing to bend to apples demands for revenue sharing. Suppose at least if they have gone with o2, a 3g iphone is surely a given, as I can't imagine they'd launch with a GPRS only handset in 2007.
I'm assuming it will be 300quid on an 18month contract at around £40-50 per month going by us prices, which is too expensive imo for the uk market.