Growing on a Laburnum tree
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Atrichum undulatum usually grows on soil and has slightly undulate leaves with vertical bands of tissue above the nerve. It’s difficult to judge scale from the picture, but this moss also looks smaller. I suspect it could be Orthotrichum affine
Sorry didn't scroll down, Tim had already suggested the same!
Lat/Lng: 53.24693, -1.91126
OS grid ref: SK060722