As I recall we saw pretty much everything without too much trouble - couldn't get a good enough picture of the White-spotted Bluethroat to be worth posting in its own right but here's a cropped version of what I did manage!
This is the Nordic form, which has been known to breed in Scotland (1985), and stretches right across the boreal zone to Western Alaska.
For whatever inscrutable reason, this seems another bird that's put off by the North Sea. Maybe the red-throated form bred in the Fens in a warmer phase?