Ling (Calluna vulgaris)
At first, this looks like Bell Heather just coming in to flower because the flowers themselves are not 'bells', they are more tubular and certainly less full than the other heathers.
Common on the heaths of Dorset but less common than the Bell Heather and Cross Leaved Heath. Ling is actually more common in the New Forest and the heathland on the eastern fringes of Dorset.
Flowers from July to September.