I doubt because of their small land area that the Scillies would ever get radiation fog, which is cleared by sun radiation or stronger wind, the fog that the Scillies suffer is basically low cloud in warm sector conditions that cling to the higher ground, the same problem that Lands End airport suffers. No amount of sun or stronger winds will disperse this, only a drier airmass.
A lot of Islands suffer the same problem, all the Channel Islands for instance...