Mystery Tits

Firstly, I must apologise, I'm not a crack shot like some people here.

But this is my story - we have a number of birds in our garden, Blue Tits, Great Tits, Dunnocks etc and what we thought were Coal Tits for the last couple of years.

Recently I was thumbing through a garden bird book I got for Christmas and realised our Coal Tits didn't match what was in the book, namely because of the big black stripe down their chests.

A bit of research suggests they might be Cinereous Tits, but I can't find reports of them in the UK elsewhere.

I did find other people posting pictures in these forums asking the same question, but were universally told they were juvenile Great Tits.

These are not juvenile birds. They're a pair and have been around our garden for a couple of years. There's no yellow around the mouths and their plumage has remained grey year round.

They don't have anything to do with the Great Tits they frequent our garden and prefer the company of a pair of Blue Tits.

I open the floor to all suggestions!