Just to update this, we were over last week and neither my Virgin or my wife's Talk Mobile phones would work there, even though she got a text from TM as we arrived telling her it would! My step-son's EE phone worked fine.

We bought two ten quid Sure Mobile SIMs from their shop in Strand Street and they did the trick all over the Island all week.

Virgin became O2 just after we returned, so we'll see what happens next time.