... I had a look ( through google images ) at some Nailsea glass ...
A lot of the images with a "Nailsea" reference have nothing to do with "Nailsea Glass". And the term "Nailsea" is too often used to describe items with "threaded decoration" - even for items where the threads are clearly machine-formed!
A search on the Board for "Nailsea" will show some earlier discussions on the subject.