I'm bumping this in the hope that Heidi or Marinka may still be able to tell me something about the company copying the Bimini flowerpot, only narrower. I've found out a bit more about Glass Developments Ltd, from this auction site, that had a LOAD of glass buttons of all ages up for grabs last year.http://www.liveauctioneers.com/item/2672172
As they say:
Glass Developments Ltd of Brixton was owned by H.R. Thomas. It began at Morrish Road Brixton, later moving to Endbourne Road, Brixton Hill. One of their most notable customers was Norman Hartnell - HM the Queen's dressmaker.
Their Glass Developments ones were marked Brixton SW2, mine just say London, so I don't know if that makes them earlier or later?
All interesting stuff.