If you've not read Most Secret War I highly recommend it. Dr R V Jones details some of the different systems involved in the Battle of Britain and it's a great book too.
Another great (although very dry) book is 'Between Human and Machine - Feedback, Control, and Computing before Cybernetics' by David A. Mindell. This goes into the fire control stuff that I mentioned, and describes how one effect of the war was to force together the different groups that were working on analogue computation.
Most Secret War is R V Jones' memoir of his personal involvement in radar, aerial navigation, aerial surveillance etc. in British military intelligence. I read it a long time ago but I don't remember it as a dry read at all - dramatic times after all.
Brian Johnson was involved in writing and producing the BBC documentary and a book. So it's not an earlier version of the same thing. The documentary is on youtube I think - a good watch, but I'd recommend reading Jones' original book.