Do cleaners in a big office block sometimes work through the night?

Yes as it saves having to work around office workers

Yes definitely

Yes - their shifts are generally outside office hours, which may include overnight

They sure do! How else are they going to clean with out getting in the way of business.

HI no they work till about 10 pm unless it is a service desk as well.

Yes. Especially when some of them spy or pry into other people's business

Probably if it's there job

Yes

Yes

depends on the staffing and the building, but janitorial work is often night shift