Well, the thing with heather is that bees are likely to travel to it because there is often not much else for them in Aug/Sept - apart form the heather, the season has long finished. Added to that, the weather in Aug/Sept can be very dry and warm and this can mean that bees can travel great distances.
Note, though, that heather honey isn't your typical runny honey and cannot be extracted in the normal way using an extractor. Having a good supply of heather may mean that you can hold back with your winter feeding.
Also, some beeks in Ulster might well bring their bees to the mountains for the heather.
Yes, been to that part of the world. Very nice.