Two little girls by the seaside

A picture of two little girls posing next to a pebble beach.

I don't know the location of this picture but there is a very impressive looking house in the background built almost like a castle with turrets, towers and a surrounding stone wall so I would think someone would be able to locate it. I'm also intrigued by the object on the beach behind them which is wrapped in a brown tarpaulin and seems to be sitting on rails - I can't think what it is.

The date is unknown but the cars and fashions suggest late 1950s or possibly early 1960s.