I had a very strange bird on my garden feeders this afternoon. (typically, it flew off as I went to get my camera). It came in with a group of Siskins and Greenfinches. It was larger than the Siskins and slightly smaller than the Greenfinches. The head was black, albeit very scruffy. My only thought was an escapee – Black-headed Greenfinch perhaps? Does any one know if they are kept as cage birds?
Glamorgan Bird Club 
Strangely enough I briefly saw a similar sounding bird this morning amongst the siskins, goldfinches, greenfinches, chaffinches and redpoll of our large roost (total >250 birds now) when they were feeding this morning (Thornhill). The bird was a rather drab dark greenish colour with a patchy, scruffy dark head – I didn’t look closely and assumed it was just a soggy greenfinch, but a passing car disturbed the birds and I didn’t see it again. I will see what turns up tomorrow morning…