Can you use computers to design them - even if you can't use computers in them?
I ask because I think it would be hard to find any company in the UK now that doesn't use computers to design engines or computer controlled machine tools to make parts accurately.
The ability to design and build pretty useful computers still exists in the UK now and electronics of some form were available even in WW2. It would make sense if you didn't have computers to build some.
The Bloodhound SSC project is possibly something you might look to to see what the UK is capable of with its spare capacity.