Its been many years since I flew the 'H routes' but .. my godfather was one of those involved in deciding the original helicopter routes over London, the venerable Martyn Fiddler has some stories to tell about it .. although I don't quite know what! Doubtless the Colonel was up to something .. probably involving humour!
The circles are airfields, the triangles indicate the helicopter routes and the 'dots' .. I'm struggling to remember. Dots used to be an indication of fuel storage tanks (though they were black on VFR route charts .. this was early 80's) but these are clearly something else.
I'm sure someone will pipe-up with the correct information.