For Ziffit they are really only interested in non fiction although I have managed to get a couple accepted. Do it when they are doing an extra 15% bonus or through Top Cashback for 10.5% cb. I have having a declutter of my house at the moment so I am not attaching any emotion to my books or cd's. The prices they offer can change and I usually check the prices on webuybooks.com at the same time and go with whoever will give me the most. I don't care if it is only 5p, its all good.Christ, well done with Music Magpie and Ziffit! I can barely make it up to a fiver on those type of things.
Also, they will collect for free if your items are over 10kg so that is handy.You don't even need to print out any labels, just write the ref number on the boxes a couple of times.