John Betjeman wrote a number of atmospheric articles in the 1950s about Broad Street and the North London, which are fascinating if you can find them.
Saturday morning office work ran down rapidly in the 1960s (guess what, we even had to go to school on Saturday mornings!), and must have had an impact on commuters now living further out - coming in only 5 days a week not 6 being a good upside. Everyone came in, not just a skeleton. Notable are accounts of the various enthusiast excursions out of and around London in the 1950s-60s; all starting at about 2pm on a Saturday afternoon so people could get along from their office.
About 1970, with a spare day in London, I took the train round to Richmond. It became a bit tedious after a while, the most surprising moment was when I discovered, from the elevated line, that Willesden Junction and the WR loco shed at Old Oak Common were actually next to one another. Both the east side platforms at Broad Street and a series of sidings north of there were in use for storing the Derby Suburban dmus, and the non-corridor stock and Class 31s, which were used for the peak GN services.
In the early 1980s I worked in a City office just round the corner from Liverpool Street, and used to go and look at Broad Street in its final throes. Still all semaphore signalling, but I believe Marylebone still was as well. I even went over to Liverpool Street early one Monday morning to see the very first diverted service via Graham Road come in. About a dozen passengers.