Medium sized yellow/grey bird with bulky bill with a seed in it sitting on a telegraph wire near a coastal clifftop in a sheltered valley
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Not 100% sure but it looks, as you say, like the bird may have a seed or something in its bill accounting for the apparent shape, failing this it could possibly be a deformity. But if you look at the birds plumage overall it is certainly more Yellow not the more green or red you would expect of a Crossbill.
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Lat/Lng: 57.658, -2.255
OS grid ref: NJ848631