The list is incomplete.
I have tried to source all components in the UK, for example carbon fibre tube, but the firms who suggest they are offering British goods often aren't, and there is no true British source. Then there's aluminium, steel, fixings, plastic, paint, tools and the rest.
We thought we had found a UK engineering manufacturer but it became clear they were ordering from anywhere. I used to turn all turned parts on a lathe, but compared with overseas suppliers I would be getting less than a pound an hour. It's exhausting and it slows down progress in all the other areas of growing a new business and working towards breaking even. Can I hire a lathe operator in London for a pound an hour? No.
The people who make parts for audio equipment generally get paid. They feed their families. They might not otherwise have a living. Trading with them is mostly ethical even if they don't like their jobs. That's work. It's a nasty business but if you need to eat...
Please put me on the list of UK-manufactured audio - I do a lot more than assemble imported parts.