Got a Galaxy S5 that is! In the end I decided to stick with O2 and upgraded through CPW - I was ignored in the O2 store (hardly any staff) so went to CPW and ended up with a better deal.
One question - they did a SIM swap instore and, while I can use the phone, I haven't got my own phone number. When I checked on My O2 my number is showing so is it likely to sort itself out?
Also, I've noticed my contract renewal date is showing as December 2017 - I presume that's something O2 can sort out?
First impressions of the phone are good, sharp screen and very, very fast processor. I'll update more when I've had a chance to play with it properly.