Teesmouth Bird Club

While trying to get photos of the Yellow Browed Warble my Wife picked out this little fellow. He was bobbing about among the grasses and shrubs and this very poor shot was the only one I could get before he left.
He had a Blue lower bellie, passing through the legs and toward the vent. Then changing to Grey and light olive Green around the vent. He had a predominantly Black head and the oddest thing was that he also had Yellow Feet.
I cant place it, so in the hands of the experts it goes.

Could be an aberrant goldcrest as they have yellow feet. Found this pic on Internet showing a part melanistic blue tit.

Goldcrest for me as well from the feet.

Thanks to Neil & Ian for the comments.

I did not consider Goldcrest because the bird had a full black head. I have never seen this in any Goldcrest. I did see more of the bird "including the black head" when I focused on it but as oft happens by the time I pressed the shutter button and obtained the shot the bird had moved and I had no further opportunity to get a better shot. I was also put off by the blue shade on the area between the legs. Again I have not seen this in Goldcrest. Never the less thank you for your input and as you both lean toward the Goldcrest, then so be it.