A little background on the Falcon Glassworks, courtesy
Old English Glasshouses, Francis Buckley* and
A History of Glassmaking in London,
David C. Watts', the latter of which has many illustrations and far more background detail.
Was thought to be founded in 1693 as the Falcon (Faulcon) bottle house, and underwent several name changes from c.1752 until c.1802. The site was not always fixed either as the works moved to Holland St in 1814 (by Green & Pellatt) and the Old Kent Road (passing 'Go') in 1877 and then to Stourbridge in 1895. Pellatt's involvement appears to date from 1803.
According to Watts, "
From the same account[1] we learn that sand for the batch came from Aylesbury in Buckinghamshire and Alum Bay in the Isle of Wight.".
David may very well be able to expand further on the source of sand. I know that sand mines were not necessarily coastally-based but, of course, land does not remain static and marine skeletons can be found halfway up mountains!

*An excellent historical book, published and reprinted by the
Society of Glass Technology, but seriously marred by the lack of an index!
1. Ref.
The Busy Hives Around Us, 1861, James Hogg & Sons