Just reporting back about
Mac2Cash
Here is a timeline of the whole process:
2 July - instant quote online
4 July - package picked up (UPS collection free of charge)
6 July - payment marked as cleared and sent
11 July - cheque received through post
I was kept informed about the whole trade-in process via its online system through email (collected, payment cleared, payment sent), which was very easy to use. Nick Gillard, who is the director of Mac2Cash, was very helpful on the email and on the phone. I was paid the original quoted value. All in all, a very professional service ran by a trust worthy company - the Bookyard.
Mac4Cash - appeared bogus to me as they never replied to any of my emails after initial contact. I would avoid them personally if you don't want to be scammed.
*Disclaimer* I am NOT affiliated with Mac2Cash or the Bookyard