Having recently taken delivery of a pebble, I packaged my almost mint SGS in too much bubble wrap and sent it off to Envirofone. I've used Mazuma before but Envirofone were offering slightly more.
They sent me an email. There was a problem. The back cover was damaged. They reduced the offer by £20. What had happened, I wondered.
I asked them to send it back. During it's return journey with Royal Mail, it healed itself, no damage. Once I had removed the gunk from the screen left by their label I repackaged it and sent it off to Mazuma. Lesson learned.
Looking on the internet I see I am not alone. People who KNEW their phone was in good order posting similar to my experience. How many people would simply accept it and take less for what 'could' be described as a scam, if anybody wanted to allege as much.
Just thought I'd pass on my experience for your consideration and I'm sure many on here will have used Envirofone without incident.