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Yes, I think you are right - especially as it is feeding on the niger seed feeder, which greenfinches do not (in my garden at least).
It is a young goldfinch - they don't have the black/white/red head colouring that the adults have. They develop the gold/black wing markings first.
Lat/Lng: 51.91821, -0.827592
OS grid ref: SP807250