They offer a minimum of 30p for CDs, 37p for DVDs and 50p for games. Freepost delivery and 10% cashback available. They typically offer 1/3 of the lowest amazon marketplace price for CDs and DVDs and 1/2 for games. Since amazon marketplace can be ridiculously overpriced, you may find one of your obscure DVDs or albums being worth a lot, so it's worth a punt. They sell under the name Zoverstocks on amazon marketplace and a few other sites.
This 25% deal runs until the end of February.