I can give you no more information, there is a paper being published and I will forward you a copy as soon as. Re: "is any land access to the mainland (I presume Ireland) during low tide?" no not as far as I know! The Islands off the west coast are very rocky (they have to be to survive the battering of the Atlantic) so I would presume the earthworm supply out there is minimal! hence the beach combing and the rabbit predation!
I wonder then how on earth the badgers ended up there in the first place. They are not exactly known for their sea-faring behaviour.