More than certainly agree, I'd only get £95 for mine.
Printable View
I always see mazumamobile advertised on TV so I would say go for them. The first one you listed is most likley safe to use though.
I'd go Mazuma Mobile because I've heard a few criticisms and bad things about Envirofone so I'm not really trusting them. I don't know about fonebank so I wouldn't be able to help you on that one, sorry!
Have you tried cex?
http://uk.webuy.com/sell/
£144 for my phone :( I see it selling on eBay for a good 200. Have you tried selling it to a shop/pawn brokers irl?
On www.sellmymobile.com the highest offered is 80.10GBP for my BB Curve 8520 by some company called Top Dollar Mobile.