The UK have a long and impressive history in electronics and speakers, but I can think of only two British headphones manufacturers: KEF and Quad (and the Quad ERA-1 is a new product).
Why are there so few headphones from the UK?
It’ll be due to many reasons.
Main one is British manufacturing and industry was killed in the 80s under Thatcher. British economy became focused on a service economy and IT. A few hifi company’s such as Linn embraced this and heavily invested into digital which has paid off.
Also seeing how small the u.k is, it’s a surprise we have any such notoriety in the hifi world.
Also audiophiles in the u.k started off from DIY electronics, which where generally a bit dodgy and doubt many where brave enough to strap some homemade speakers to their ears