could be as late as 8pm to 10pm at night.
I remember I had to go back once.
Anyway, you can walk between the MC ones in 10 minutes so you dont need much time.

Something that no-one mentioned is that you will need your passport to enter every casino in Europe.
They may or may not charge you entrance fees outside UK. I have rarely ever been charged but that might be an EU thing.

Did you check that hotel in London I sent you?