David Sinclair wrote:
Can anyone tell me where I might be able to obtain recycled glass sand
in the Swindon, Wiltshire area?

What do you mean?

You can get hold of bottles anywhere these days from a recycling point
if you ask first, or from a nightclub following a busy night. Put them
in a cement mixer with some engineering bricks or similarly sized iron
scrap to crush them.

Is that called cullet? Not what you are after though?

"The Liquid Glass Centre is part of a complex of craft workshops
situated at Stowford Manor Farm in the heart of south west England. The
Farm lies between Wingfield and Farleigh Hungerford, in the picturesque
rolling valley of the River Frome, where Wiltshire meets Somerset."

http://www.liquidglasscentre.co.uk/home.htm