I have a meeting with Ferranti next week about some projects, I will bring up the ULA for the C5 to see if they have stocks, If ever I have needed discontinued parts these guys have always been able to source them. I got a guided tour a few years ago of there stores and they have so much stuff that has been shelved from old projects.
Who knows! I might strike lucky, If they still have the source they will probably be able to do a run.
The problem is Plessey had a hand in it too, but the ULA was fabricated by ferranti so stocks may be available.