Reading all these comments, I'm reminded why I favour outcalls these days. Once the girl shows up, that's it. Clock starts. And it's in her interests to show up promptly, and ready. She can have a couple of minutes in the bathroom to get changed, powder her nose, or whatever the fuck they do in there, but that's it. And when the time's up, they can leave.
I hate all this time-wasting malarky as much as anyone, especially the constant leaving the room for stuff. How long can it possibly take to stash the cash in a jar in the kitchen? Or pee? Or put some stockings on? Outcalls obviate all that.
And with a bit of forward planning (sometimes none at all) you can get a decent room even in central-ish areas of London for under 50 quid. OK, so it whacks the overall price up a bit, but factor it all in, and for me anyway, it comes out worthwhile.