Only just found this thread, very interesting.
Re the concrete filled noses. I recall as a civvie instructor with the ATC of being on an annual camp at West Raynham in 1976 when I overheard a short conversation between a nav and a cadet who was known for his single cell brain.
"Mister, whats that funny shaped nose for" pointing to a TT19.
"Its fitted with Blue Circle"
"Cor, whats that"
"Can't say without shooting you afterwards" (At this point we hoped he would)
Net result was the cadet always thought he had seen a top secret aircraft.