Hi Andy,
The gentleman that you met was probably Steve Webb, a true gentleman. Unfortunately Steve passed away 18months ago. He was a very good friend of mine and a member of the association of model Submariners. The Chariot is still on the model boat circuit now being run by his wife at selected events.
The frogmen suits are getting a bit worn now but it still operates very well, the model won a silver medal at the Model Engineer Exhibition in 2001/2002
Robert Hobson is the founder of the Underwater Heritage Trust who have most of their exhibits in the Eden Camp museum in Malton North Yorkshire. There is a full size Mk I chariot, a Mk II and the Italian Maile in this museum.
There are others who have built chariots that I know but Steve was probably the man that you met.
Regards Alan