Tubes and Valves - Transistors Yuuuuukkk
Valves or Tubes in the U.S are very very easy to get. One previous poster thinks they have gone out of fashion. The fact is they are better than the modern equivalent in many cases. Langrex down in Croydon still have and buy in stock from all over the world. Many shortwave transmission station use valves and being a radion amateur myself still use them.
Apart from dropping them on the floor they are a lot more rugged electrically speaking as they physically move electrons through a near vacuum, with a few gasses as opposed to a solid substrate.
Listen to any valve radio and then listen to its modern equivalent. Modern ones just just rubbish by comparison.
Going back to an article done by the late Paul Young for Everyday Electronics in the 80's, when he was lucky enough to meet the boss of Sony (I think), even the boss (in Japanese) agreed.
Why do you think places like Maplin sell a Valve Amplifier kit ?
Good luck to those at Bletchley - Keep up the good work !