to be honest with you , I have just done it , the deal has tracked at ?50 and pay out date is the start of june , as long as the contract is paid and not cancelled I should think I will be ok , I ordered the phone Saturday afternoon and it should be here tomorrow , quidco basic account showed the ?50 within 2 hours but they wont pay me until the start of june , I will put the sim card in it , get it unlocked , wait a week or two and pay of the ?240
as I haven't cancelled the contract but paid it off in full I would expect to get my ?50 cashback ;-)
edit - sorry everything is done through o2 , you just click a link on the quidco site and it takes you to the o2 online store , you make your purchase and it should track the order because you used quidco to link you to o2 , so the phone tariff etc is all through o2 , the cashback is all with quidco , quidco only pay out if you don't complete the deal , I would think that paying out the contract is completing the deal whether they beg to differ is yet to be seen ;-)