It seems the days are long gone that you could buy a new pay as you go phone and transfer your old simcard over and gain a reward.
Just tried o2's new phone upgradehttp://shop.o2.co.uk/Mobile_Phone_Upgrades
The operator informed me my loyalty for the past 3-4 years is that i would receive a £9 discount on the sony erricson W395 OR a top up reward of £18.55
Phone cost calling phone upgrade £59.99 reward discount £9.15 or balance reward £18.55 again much more than the price online
Same phone £40.00 for online customershttp://shop.o2.co.uk/mobile_phone/specification/Sony_Ericsson/W395