Twittering Flittering

This is one of a family of several little birds flitting around the roofs and piping a twittery song. I am pretty sure they are wagtails, but not sure which sort. Any ideas? (Wondered about 'black headed wagtail'? Don't have my bird books to hand.) I used a 'burst' setting on my camera to get these in-flight shots.

Another lovely family day!