Hi Manna.
I don't know how I've managed to miss your blog for so long. I've just read the whole thing in one go and it's fascinating seeing how the layout has developed over the years. I've always wondered why no-one has modelled Edgware or Barnet and all the time you've been at it.
Yoe may know this and if so I apologise but the very first edition of 'British Railways Illustrated Annual' back in the 90s had an excellent and well illustrated article covering all the Northern Heights branches. It was written by one K. Coventry and had track plans for most, if not all, the stations. I recommend it to you as it's full of information for anyone interested in these lines. If you've not seen it you might be able to get hold of one on Ebay or a specialist bookseller. One edition of the free LT Underground maps, published shortly before the war, showed the whole Northern Heights network and the Elstree South extension as part of the Northern Line although it was marked in hatched lines representing "Under construction".
I grew up in Middlesex, very close to the 'Northern Heights' area. If you stand in certain local vantage points on a clear day the views, even today, will show you why the area was so called. My mother moved to the area in 1928 when she was 5. It was being 'developed' at that time but still quite rural and even in the 60s I passed thatched cottages every day (in London NW9) when I cycled to school. She could remember the night the Crystal Palace burnt down and because the area was high enough they were able to see the glow in the sky 15 or more miles away.
When I was 11 and 12 a regular summer evening escapade with another train and bus spotting friend was to cycle over to either Colindale trolleybus scrapyard or to Edgware goods yard. I can't now remember how we got in to either place but of course there was no security then. We spent ages messing about on the old trolleys or pulling point levers and clambering over goods wagons.
By the by, shouldn't your bus be an STL, rather than an RT, which didn't enter service until after the war?
The blog has brought back many memories. Great stuff mate.