It came to the bird feeder for several weeks and the reddish head got steadily paler
No interactions present.
I think it could be a hybrid between a Goldfinch and Siskin.
These were quite commonly bred many years ago: I would not be surprised if that still goes on.
I don't think they were that commonly produced "many years" ago - they couldn't keep wild birds alive long enough and people caught whatever they wanted as a cage bird from the wild.
Breeding hybrid/mule show birds is very much going on - it is probably as popular now as it has been for very many years.
Lat/Lng: 51.5, -2.5
OS grid ref: ST6979