What is it?

Can anyone help me identify this little chap? He is new to my garden and I had assumed he was a sparrow until I saw him on the screen. Now I am not so sure. I have been of the RSPB site but that has just confused me more.
He is incredibly camera shy so I have been stalking him for about a week. In order to take this I was sat behind closed curtains with just the camera lens poking through!