Tommy Flowers was keynoted in my time as a student across the 70s and 80s, and was mentioned by Hodges when he toured his biography of Turing. (I saw him speak over a week at Leeds university) I grew up with people (obviously far older than me) who had worked with him. He's all through Hodges' book and from memory, he's in other histories of Bletchley.

He's well known in computing history circles.

The story of how the Post Office got involved in building out the systems used by GCHQ, and the post-war dumping of supplies into a research market bootstrapping the digital computer advances was well understood. ICCE (for example) the Imperial College numerical engine built in the 50s, was a relay machine made with war surplus post office relays, because valves were too expensive. The amount of relays coming onto the market post war was very probably a signal of technology transition inside the GPO. Why did they have so many relays surplus to demand? Telephony was surging! Strowger Switches (which use relays) were the backbone of telephone exchanges right up to the 60s.