I go to the one at grindon. Rarely packed at any time but it is getting busier. Got basically all you need and there's rarely a wait for the things you need. Only 3 treadmills and one bike and spin bike so sometimes cardio is a struggle but barring that I couldn't recommend it more
People lead different lives nowadays, lots of people work outside traditional working hours. I've used puregym "early" at 4am and "late" at 2am , it's obviously quiet but usually a few folk in. Quite a lot of foreign students seem to use it at those times I have noticed.
Also many more people are starting work earlier now, traditional hours aren't usually any earlier than 6am and a lot of people go at 5am now.