I think you'll find that Starbucks are opening an outlet on Rockall in
the next few weeks, as it's the only place in the country that doesn't
have one yet!

as it is not recognised as habitable land despite the efforts of an
ex-SAS man who camped on the rock for a few weeks.

You're right about it not being habitable, and despite the SAS camping
trip, i don't think anybody claims it is, even the UK. As an
uninhabitable rock, it has no effect on the allocation of exclusive
economic zones or continental shelf rights, and so nobody really cares
who actually owns it. Britain annexed because of the rocket testing
thing. Furthermore, AIUI, Rockall just falls within the UK's EEZ, and so
it gets too look after it in terms of mining, ecological protection, etc.

tom