In reply to Bottom Clinger:
Helvellyn, Fairfield and the Scafells have typically been my most reliable places to see them in England but I haven't had much luck in recent years, except for a flock of a dozen on the summit of Ingleborough on an otherwise truly miserable Christmas Day in 2022.
Certain places in Scotland are more reliable for sightings as there is a small breeding population as well as birds that spend the winter. In England they are merely winter visitors and will soon be off to their arctic breeding grounds. They also often turn up on the coast, particularly North Sea coasts.
As Phil1919 says they are remarkably well camouflaged and will often not move even when people walk very close by. I only spotted this little group when one of them moved.