"Never seen an RCA TV in the UK, and I think the GE ones were co produced
with Hitachi. "

Here, Hitachi and RCA had quite the relationship. They built bigscreens for each other. You could open up an RCA and find a Hitachi or open up a Hitachi and find an RCA. The last two it seems were Mitsubishi and Sony if you actually wanted their product, everyone else eventually would just buy whatever and have it rebadged.

"One of the setups with RCA tubes used a low voltage flyback system - it was
hard to get transistors that could handle the current. "

Did not run into that problem. I did have some small Emersons that were hard to get a damper diode for because it was such high current. But not an RCA. But you said RCA tubes, that is not the fault of the tubes. It is the fault of the engineers.