The Sony Ericcson w880i has been reduced from Â£179.99 to Â£149.99 in all o2 shops. When you buy the phone it comes with a 3G sim and you have to buy Â£10 of credit.
However if you tell them you have a non 3G sim and plan to port your number to the sim included in the box, they cancel off the required Â£10 AND knock you Â£12 off for being an existing customer! They ask for your number to check you are a current customer but don't (and can't) action the port (only o2 customer services can do this).
This is THE cheapest way to get a w880i on o2 PAYG (black or silver model). The phone comes with 1GB Sony memory as standard too.
This works if you are buying as a gift for a non o2 customer - you don't HAVE to port ;)
(You can get the phone another £10 cheaper if you trade in your old handset!)