Blackberry Bold 9000 (3.5g, WiFi, GPS, 2 megapixel) FREE on O2 with:
Unlimited Data Usage
Regular price £30 p/m, take the offer with 16 months half price line rental + go through Quidco for £50 cashback. Total monthly cost is then £17.91.
The half price line rental is by redemption, meaning that every 3 months over the contract length you have to either post or email a copy of your phone bill to confirm you're still on the same tariff. Money Saving Expert have a free tool that emails or texts you 6 weeks prior to the due date to ensure you get it sent off in time.
Seems like a pretty sweet deal to me, considering most Blackberry packages from networks cost in excess of £30 plus extra for email boosters and whatnot.
Mobiles.co.uk also offer next day delivery if you order before 4pm I believe.