As was mentioned there are no B&Bs, it's camping or renting one of the properties. Camping is relatively cheap, the houses are pretty expensive unless you can fill the barn (there was a big wait for the barn last time I checked.)
In reply to Southern Man: You don't actually have to self cater as the pub does great breakfasts and also evening meals, the shop caters for stuff to make sandwiches for lunch.
Actually May might be a good time to go as the full Island isn't opened up for climbing until August, though if you've never been before there will be plenty of cliffs open in May. Check with the warden at the office when you arrive, sometimes even the ones in the ban will be opened to climbers if the birds haven't chosen to nest that year (conversely some not banned may be banned if the birds have nested, you have to check withthe warden).