Lee, You mention EASTERN YELLOW WAGTAIL as having not occurred in the UK this year. It seems then that you have overlooked the two records from Shetland this autumn, both very well-photographed (by Michael McKee & Robbie Brookes) and at least one sound-recorded. See images here. Michael's shot especially is superb.
http://birdingfrontiers.com/2011/10/28/magic-words-eastern-origin/wagtail-sp-2_1-r-brookes-2-resize/http://www.michaelmckee.co.uk/regionview.asp?ID=1852&Region=Shetland
James Hanlon