Dosent the law say you have to refund postage costs under DSR ?
That's a nice gesture but can I suggest something if you want to have the best etailer customer service in the UK?
Drop your premium rate phone number, nothing says "we don't want you phoning us" like a premium rate number that calls 10p a minute to call!
At least two of your major competitors use 0871 as well so that would certainly be seen to the world at large as a plus point.