08454 04 05 06 will be your best option,but it is Christmas Eve. I got through to them in 2 rings last week. Excellent service.
a quick search has not turned up a direct answer but basically, you have not received anything so you have no need to pay. It seems as if the seller has agreed that there is no delivery, you have the right to cancel the order in any case, so just claim your money back under this click here see if things go wrong.
I am no expert but feel the seller is the one with the Royal Mail contract, will the Royal Mail let you speak for the seller, I doubt it and why should you.