Lovely little birds, there's been odd ones on the South Coast in the past few days too. I bumped into a group of 4 on the Cornish cliffs a year or so back- heard an unfamiliar call and there they were- very tame as per usual. Saw quite a big flock(40 or more) on Winterton Beach in Norfolk once, they looked like a blizzard...but I don't think you can beat seeing them in summer plumage in e.g. the Cairngorms.
@Pertinax Yes, I've seen them at Cairn Gorm itself a couple of times and they really look the part there (was the first place I ever saw them, as a teenager on my one-and-only skiing trip!).