I guess it is a geology thing - a subject of which I know nothing.
But we spent a week in June at Studland Bay in Dorset on mile after mile of beautiful sandy beaches. This was at the beginning of the heatwave and it was just perfect. And we have just returned from a week on the Norfolk Broads - and again the beaches at Sheringham, Wells-next-the-Sea and particularly Gorleston are incredible. So why are the beaches in Sussex so pony? Is it to do with the rocks or the tide - or a combination of both? Seems odd that just round each corner the beaches are so spectacular?
At a bit more than a guesstimate I would say the chalk landscape has been eroded by the sea and then has dissolved whilst the Flint is too hard to denude quickly. Leading to a load of Flint pebbles rounded by the movement of the sea.