Worth remembering that heather moors are really large boggy water sinks. It may be dry on top but underneath there is still a lot of water. I'm looking forward to seeing what the crop is like this year as it will provide a lot of info on what is required (or not) for a good heather crop. Last two years we have had very wet June's and July's and exceptionally good weather in August which has given bumper crops.
Is it the foraging weather? Or the amount of rain in June/July?
Seeing the staggering amounts of honey being brought in with our long extended hot dry conditions my money is on the weather.