Looks like a Grey Wagtail to me.
No seriously, I think an immature Rosy Minivet either nominate or stanfordii must be a strong possibility (let's wait for some expert comment) but as hybrids are said to occur, I guess it will be difficult.
Maybe I will have to queue for the ferry tomorrow.
[ Last edited by wgeoff at 11/10/2010 13:16 ]