Actually I have a serious idea, now that Cirl Bunting has been mentioned again, and seeing that the OP wondered if it might be a Cirl Bunting or Yellowhammer . . . . (that's been mentioned on threads, the person seeing the bird has a lot more experience of the actual bird . . .)
The more I look (always a bad move lol!), the more I see Cirl Bunting here . . .
Would explain the more 'front heavy look' some are seeing.
Those tail sides, well they could be grey, not convinced they're white myself.
Chestnut shoulder patch
Two toned bill
Strong white wing bar with dark centres above
Would explain the pale spot at the back of the cheek
Would explain the strong russet UTC's
Would fit the habitat and posture of the bird
The photo shows a) Yellow tones b) Chestnut tones c) White tones in all the right places - from this I'd think they were all real and actually present.
We think the whole pic is a bit washed out (the branches are paler than they should be), so what if it is a washed out looking Cirl??
From the Collins (couldn't find any images of 1st w Cirls on the internet myself - looked in the gallery here, there's about 50 adult males and 3 females, 0 immature/1st winter not helpful at all!!!!!!), does fit.
Problems are the face may still be too darkly marked, and the breast too white (in which case it's a hybrid cirl/reed lol). Also do they have a crown stripe?
1st W male Cirl Bunting - washed out photo- would it look something like this? At least as much as a Corn Bunting!! and as much as a Reed Bunting??!!
Distribution; well a Cirl Bunting at this end of the country is as likely (more?) to come from the continent as the south west, and yes they do turn up as migrants.
So there you go!
(No one has to agree with me, and if no-one can see what I mean then so be it. . . But how else are we going to get to 5 pages??!!
) Seriously though . . ??