Sand Martin`s holes, birds were far too quick for my camera but were very busy feeding above the stream on the beach.
No interactions present.
Despite you seeing them going in and out there are a few clues which would indicate these to be sand martin.
Firstly, the lack of any debris in the entrance shows these holes are most likely to be being used.
There is no evidence of any kind that a mammal is moving in or out. You would see grooves, claw marks etc. where the mammal formed a trail to the entrance.
They are near the top of what appears to be a fairly steep, sandy cliff; hard for a mammal to reach it, though not impossible.
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Lat/Lng: 51.6433, -4.8045
OS grid ref: SS060975