No, they're French. Quite a nice little cafe I believe, but I was so knackered when I got there that we never got the dinghy out to go ashore, so I don't know.
Chausey is an island in the 'Channel Islands'. You clearly believe that the 'Channel Islands' are part of the archipelago called 'British Isles', thus Chausey is part of the British Isles. The use of the word British in the name of the archipelago has nothing to do with political or legal ties: after all Ireland is in the British Isles, and the Irish don't much care for the term. In official circles the term is falling into disuse, partly for that reason, and partly because nobody seems to be able to agree what the term 'British Isles' means.
I have a letter from a well respected historian with several learned books to his name in which he argues that 'British Isles' includes Chausey, the Danish Faroes, and the German Heligoland, amongst others!
For the record, I don't include the Channel Islands in the British Isles. Just look at a map. We are clearly off-lying Normandy, and it makes no sense to me to bracket us with the British Isles.
Have come to this thread late - not much to add to what has been said. I would say that they are well worth a visit. I would particularly recomend at least a day trip to Sark - even if you are not comfortable anchoring up for the night or two - maybe a bit quiet for the kids, but if you hire bicycles at least you can tire the beggars out!