well, in Sweden both Calluna vulgaris and Erica tetralix are very common and range all over Sweden. Erica tetralix is more of a bog plant then C. vulgaris, though both can be found in wet-dry habitats. This one on the other hand is only found in the mountains in northern Sweden.
So I didn't think this one would be found on the british isles, but on the other hand - islands can be quite mountain-ish when it comes to habitat. XD
thanks for the information, yes Bell heather erica cinerea can be found here in the north west highlands of Scotland, it prefers a drier location than calluna vulgaris, can find it dry knolls on the peat