But my impression of London (from living there for a few years in the 2010s) was that it is very much a 6am-11pm city and everything is shut at night. Surely infrastructure work can take place during night shifts?
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.
It's a bit later nowadays, at least in the normal sorts of places you'd go out (Soho, Shoreditch, etc.). Though, what are you doing working until 11pm?
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.
I no longer do - working in the City wasn't for me. And neither was living in England. A week in the summer and over Christmas turned out to be just the right amount of blighty for me.
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.