I've been waiting for symmetric fibre for a year, and they're trying to install it, but getting the permission to close the road to lift up the manhole is proving to be a challenge.
Traffic management and road closures can be hard work, we've had to wait over a year before for a road closure as it would affect multiple bus routes. (And as an aside, lockdown was extremely productive for network build like this!)
I found the experience of working in the city and living in Westminster frustrating, because shops, public transport and even pubs(!) would effectively have closed by the time you finished work.
In any case you'll still find the roads can be busy at all hours. The night is used, as you say, for a lot of infrastructure type stuff which means the main roads are still busy, getting the city ready for the next day.