Holkham, North Norfolk
Horse rider on Holkham beach with naturist area in the background
The nicest beach I know of in the UK, it looks more like the west coast of France and doubled for the Caribbean at the end of the film Shakespeare in Love.
Parking is in a road opposite the entrance to Holkham Hall and the naturist part of the beach is at the left hand end. The unspoiled beach is approached through pine forests and sand dunes, though naturists are asked to keep out of both (they had trouble with the anything-goes brigade).
Even when the tide is right out, the whole beach is clean sand and the only drawback is that it is exposed to cool northerly winds, so you might need a windbreak.
To save yourself a long walk along the sand, when leaving the car park look for a path on the left signed for the nature reserve. If you follow that you come to a bird watchers' hide on the right alongside a boardwalk which leads down to the beach. That brings you out only about 150 yards from the beginning of the naturist beach (turn left).