Sony Ericsson K800i Brand New (3G phone)
Got it as part of a new contract but i'm happy with my K750i
It is on O2 which i believe don't lock the phones, but I don't have any spare alternative network cards to test.
You can also use normal sim cards with the phone but you don't get the video calling facility with these.
Looking for about £300 for it
Based in Croydon so can drop the phone off anywhere between there and central London