Hi Keith
I have just read through this thread and the other one you posted about Royal Brierley. I agree the canes in this weight are Murano and the canes were readily available as they were (and are) openly traded by the Murano makers.
Almost certainly the problems Royal Brierley had were caused by incompatibility of the Murano canes with the glass they were using. The COE for the two glasses only have to be very slightly different for there to be annealing problems. Some colours are more prone to this problem than others, white being the worst offender. Paperweights need longer annealing time than thinner glass products but this is usually only overnight.
You pointed out the connection to Devon and just over the border is Liskeard Glass. They were founded in 1970 and had links with Isle of Wight Glass. They made paperweights in their own name and many of the designs were made using Murano canes. They also used to make paperweights for other firms including the Yelverton Paperweight museum.
Liam Carey started his apprenticeship at Liskeard Glass in 1977 and eventually bought the company in 1983. He renamed it Merlin Glass and he now concentrates on high end glass door knobs and furniture knobs. Interestingly some of his products still use Murano canes. Might be worth contacting him to see if Liskeard Glass had any connection with Royal Brierley.
Hope this helps
Derek