As im sure you know top cash back are doing £150 cash back on orange mobile contracts, so using http://www.hotukdeals.com/deals/get-10-off-your-orange-mobile-phone/768771#comments
you can get some amazing phone contracts>
Free HTC Desire - Dolphin 40 ( 800mins Unlimited text, internet) effective cost £25.41 18 months (37.5-10%) and £150 TCB.
Free Samgsung Monte / Nokia X6 - Dolphin 30 (500mins unlimited texts, internet) effective cost £18.50 24 months (27.5- 10%) and £150 TCB.
I understand TCB cant be guarenteed, and you have to meet the criteria to get 10% off - well either work for or have a friend or family member who works for NHS, Military, Local goverment, Teacher, and loads of other companies - see other post.
I think this is a superb deal: £25 a month free HTC Desire with 800mins, unlimited texts, 3gb internet on a 18 m contract.
This is a £37.50 a month tarrif for £18 months True cost of contract is £675 for the 18 month peroid.
Cashback is not a garuntee.