On balance I thought the programme was quite good and certainly worth watching. Yes I would have liked more on the technical background ... but that's just me I guess. Probably a bit rushed at the end in terms of integrating RDF into the Fighter Control infrastructure ... but it was badged as a drama and needed to be watchable/engaging for a majority.
I'm sure there were excerpts from the Battle of Britain film used in the making of this production
Here is the OU follow-up link ...
OU on the BBC: Castles in the Sky - OpenLearn - Open University
Interesting info provided by the OU ... See ... Radar: What happened next?
Coff.