Firstly credit must go to IrishGypsy on MSE for finding this one.
I went to the Virgin Mobile stand in Zavvi in Reading today and got myself a brand new Nokia 1112 for only £2.50. This deal is for existing Virgin PAYG customers - I had to give my Virgin mobile number. You get no simcard & no credit but you do get a brand new phone. The phone costs £7.49 with a sim.
CeX are paying £10 for this model (on Virgin) or £15 if you get it unlocked (or you could get a bit more on Ebay!).