If you order a sim only deal from 02 such as the plan for SmartPhones, with
at £20 a month
you get £120 TopCashBack cashback so
£20 x 12 = £240
£120 / 12 = £10
Good deal imo.
Ends tomorrow so be quick!http://shop.o2.co.uk/tariffs/simplicity/smartphone/12_months
EDIT:Topcashback offer £200 on £25 a month contracts so if you trust them to pay out you may get a better deal, but if they don't you are stuck paying £25 a month.