I saw the project at Bletchley in 2005.
The GCHQ had imposed conditions like the machine had to be behind a glass screen so the public could not get close to it, and a small section of it was still banned by GCHQ from being constructed although they were hoping to get permission at any time.
It suprises me this stuff is still secret, after everything about cracking the Enigma etc that has come into the public domain after the initial revelations c. 1980. One book I read (West?) was particularly detailed in the description of the methods.
I guess the builders of the current machine had to be sworn to secrecy. Looking at Tony Sale's
website he may have been banned due to this.
Valves are not a problem. The Russians for example make loads of valves. A lot of them go into high-end "hi fi" gear - the Russians must be laughing all the way to the bank flogging bits of glass (with gold plated bases of course) at £20 a time to the stupid Westerners who think they give superior sound.