Caporegime
Send it back under DSR. They have to cover postage, and can't charge you restocking fees.
They don't have to cover postage fees on a DSR, they do on a return for fault though.
The only postage fees you can reclaim on DSR, is the amount you paid to get the item to you in the first place, but I can imagine that a lot of resellers would tell you to do one, and it's not really worth having a massive argument over a couple of quid.