Siberian Chiffchaff

Or at least I think it is....Someone may tell me otherwise but after more time than I have to spare, trying to ID it, I hope I'm right.

It's been around the garden for a couple of days, flitting around like a wren for insects but is strangely unafraid of my presence, hanging around nearby even when I'm walking around.  It looks like a Chiffchaff but it's legs are too dark and doesn't have the yellow and greens I would expect to see on it's head.  

Someone help... ornithology is not my forte beyond the most common species!