Hi David - Al Thorneycroft often signed his weights like this or AJT and I have never seen one with a label. I think he worked at the London Glassworks then became a teacher in glassmaking at the University of London
My recollection is rather hazy and I am not sure which of the glass studios in London you mean, Dave, because unfortunately over the years people have not been entirely imaginative in their choice of names: The Glasshouse, London; London Glassblowing Workshop; Glassworks, London; as well as London Glassworks, to name but a few.
However, I think that Al was the technician at what used to be called Middlesex Polytechnic from at least from as early as 1982, up to his retirement, but I cannot be sure of this. I think they changed the name to Middlesex University at some point.