Welsh lenses were a surprise to me too! Briefly I have two marked PPE and this is nothing to do with safety, but refers to their manufacturing, which was collaborative - Pilkington Perkin Elmer. Pilkington were a glass company based in St Asaph in North Wales. Perkin Elmer are an American optical company. They collaborated on some photographic/copying lenses in the early 1970s and I have two of these made in St Asaph. One is being refurbished by someone (in his spare time) who works for Qioptic which is the descendant company and still based in St Asaph.
The British lens manufacturing 'family tree' shows a convoluted and intermingled tangle - Pilkingtons and Chance, Ross and Dallmeyer, Wray, Beck, TTH (Now Cooke) and more were often connected through marriage (literally at times) and through absorbtion into the Rank Organisation (who imported Nikon). Irish lens maker Grubb ended up near Newcastle where a descendant company is still in existence although I think that it is now an optical coating specialist.
So far I have Welsh, Scottish and English LF cameras and Welsh, English and Irish LF Lenses so I'm trying to find an Irish camera (many were badged as being sold in Dublin (Grafton Street) but I'm looking for one built there) and Scottish made lenses (not sure here - Lizars?) so if anyone has any information I'd be interested. Part of my (very long term project) is an intent to use both cameras and lenses in the countries they were built in - it IS a long term project!
I give talks (just back from giving one on Underwater Ireland to the Royal Dublin Society) and one aim is to sort out a history of photography talk showing the influence of the makers above on photography and more besides. A Grubb lens was used by Carleton Watkins in Yosemite for example to take photos on his 'Mammoth' camera, which were used to influence Congress to protect Yosemite Valley. The 'connections' are fascinating.