I've just loaded up on the most powerful ones in NY last week. They cost about £55 a box for 20 packets so about £2.75 per strip. Just had a look on eBay and there aren't that many authentic looking Crest ones on there - there used to be loads. I was thinking of selling some myself but looking at the prices - sellers are selling for less than I paid so possibly are buying them wholesale somewhere? or are knockoff Which doesn't help you much OP but I would try and find a US seller that will ship to the UK. And thanks Mitzy for the tip - I'll have a look there too!