Birdman Grasshopper?

The shape of the control bar suggests that this is a Birdman (of Marlborough in Wiltshire) Grasshopper. The sail pattern indicates manufacture in late 1974 or early 1975. Later Birdman standard rogallo sails were chevron-cut and famously ripple-free. (Alternatively it could be a home-made sail applied to a factory-supplied frame.)

Possible location: The bowl at Monk's Down.