Blue tit - Parus caeruleus
This little chap was about to launch itself towards a bird feeder. It had spent several moments checking the coast was clear. They move so quickly, quite jerkily too, hard to catch the focus, especially on a dull day.
This is a Blue tit, Parus caeruleus. The ones in our garden seem quite pale, the blue only showing bright when it's sunny. I don't know if it's a very local thing or not.