Help? No idea.

Saw this bird on my feeder today, admittedly new to the game. I’ve tried using the RSPB interactive tool to identify the bird with no success, unless I tripped up somewhere. First thought before consulting the tool was that it could be a dunnock but it doesn’t appear to match up with similar images of dunnock online.

If it’s really obvious then my apologies....!

If anyone can suggest a good way to identify birds easily (or more easily) please do, I would be grateful to learn. 

Thanks in advance.