After reading the reviews it seemed that whether or not you were satisfied with the product was wholly dependent on the seller. So this is a review for both seller and product. I decided to go with K.K. Electronics, because at 50,000+ reviews to still have a score of 98% they must be doing something right. Plus whilst not the cheapest, they were still in the middle range of prices. The item arrived well packaged, quickly, it was new and by Design Go (to me, a recognisable brand).
The adaptor worked perfectly, but then I'd already checked that the camera charger I was plugging into it, could take the UK 240v. The two US pins also fit correctly into the back of the adaptor. Overall an excellent product from an excellent seller.