Just to put a final nail in the coffin of the Sunne in Splendour saga, I received an email from the seller:
Very good of them, I thought, but there are a couple of problems . . . mainly that I didn't keep the packaging so can't do the 'return to sender' bit, and because the book is so thick I doubt it would fit in a letterbox anyway, so I'd have to pay for postage and packing myself, which I'd already worked out would cost me around £4, so long as I didn't want it tracked.
So, in the end, more hassle and expense than it's worth. The paperback will be going to the Cancer Research Shop on my next visit.