My missus worked at Envirofone about 4 years ago, which is of no help at all i realise, but i thought it was interesting. The owner at the time who started the company was a greek guy, and he'd always be having staff nights out where he'd buy everyone's drinks thinking he was the big man... but i always chose to pay for my own.
Anwyay, i would check on the CEX Exchange website what they'll offer for it, and then you can at least drop into your local branch in person and sell it to them. Less risky and they seem to offer at least as good prices as the others in my experience.