If left unchecked, Common Gorse Ulex europaeus (left) grows into very large bushes and soon crowds out the more delicate heathers.
Its relative, the Western Gorse U. gallii (above), doesn't seem so vigorous due to its smaller size. However, it soon spreads through heather stands (as can be seen above), making it difficult to control.
At Buxton Heath we either thin-out the Western Gorse with loppers, or mow the affected area completely so that the heather can regenerate from seed.