Not a good photo I'm afraid. Maximum zoom and taken too quickly because the bird was flitting around on a dry stone wall. I'm not a bird chap and don't know what it is. One possibility came up from leafing through a bird book, but it's an unlikely one so I'm posting the photo in case anyone does know.
We saw a pair of them up on a hill opposite Monsal Head on Wednesday. Here's the second photo which unfortunately is no better.