No interactions present.
In the last decade it has emerged, largely from ringing at Slapton Ley, that M. alba ssp. alba, White Wagtail, is a common migrant through this country and also winters here in good numbers. Some seem to be from Iceland, and some presumably from mainland Europe...
Pied Wagtail is M.alba ssp.yarrellii.
In East Yorkshire, there is a reasonable roost at the school where I teach and there are often obvious alba wagtails here, though only ones or twos and only in early spring or the autumn. They are very pale grey, as David says, above.
My Flickr photos...
I'm far from convinced that this is ssp. alba, for one thing the flanks on this individual can be seen to be extensively marked with grey which is a similar colour to the upperparts (and seems to be a shade darker than would be expected on alba). I think that the apparent lack of any obvious black colour on the rump is an illusion - note that the tail and the centres of the wing feathers also don't appear particularly dark (although they would be almost black even if this is alba). In my opinion this is probably an adult female Pied (ssp. yarrellii), but it is safer to leave it identified as just Montacilla alba because racial identification is not easy from a single photo (unless the photo is very high quality and from the right angle!).
I have 3 more photos of the same bird which I'll try to put on ispot as Pied Wagtail 2. I don't know if these photos will make identification easier.
If they're of the same bird, you can edit this observation to add the pictures here
Record your ladybird sightings!
Lat/Lng: 51.5875, -0.1186
OS grid ref: TQ304893