Help with sexing needed, thought I had a pair

I thought I had a male and a female Pied wagtail visiting me, but after Sparrows post I'm not sure now, its very confusing, This one I'm sure is male, please put me right if I'm wrong.

And this one I thought was a female, that grey you see up the sides goes down the back too, unlike the other one which has a black back, but there is alot of black to her/his throat this is what is causing my confusion, I thought you could tell by their back colour but seeing Sparrows post this isn't the case, and as I've said I'm confused.

There is a sufficiency in the world for man's need but not for man's greed.