Huge mouth very yellow. No feathers
No interactions present.
It is imposible to say at so young an age - probably 3-4-5 days old. Judging from a guess at size, it is unlikely to be a finch, so that leaves blackbird, thrushes and starlings as most likely.
Lat/Lng: 51.471310964545, -2.5885516405106
OS grid ref: ST592748