If you are interested in Pendine Sands you should try to look at copies of a couple of magazines - Motor Cyclist and Motorcycling - they are held at Colindale (British Library Newspaper Library) in London. A lot of sand track racing (from reading one of these mags for 1926) was not like speedway racing - rather it was like the modern enduro events without the ups and downs. Tracks had 1 or event 2 + mile straights with tight bends at each end and races lasting for many miles. Oval tracks or circular tracks were the exception rather than the rule I think. Pendine, I think, probably was one with long straights and very tight turns.
I went several times to see motor cycle racing at Pendine. My uncle, Leslie F. Griffiths (who had ridden for Cardiff speedway team pre 2nd World war, raced there on a 1937 Manx Norton against such people as Fred Rist, Denis Parkinson and Reg Dearden. After Rist beat him one year on a BSA Gold Star, he modified the Norton to allow him to corner it like a speedway bike, and also was loaned a newer works model (as raced by Rex? Young) and he beat Fred Rist. He had a very bad crash when, after the down tube of the frame of the Norton broke in practice, he was loaned a Vincent Black Shadow by Reg Dearden, was leading at the end of the first lap, but locked up the front brake which dug into the sand and catapulted him 30 yards down the beach. I think this was probably in about 1956 or so.