Just an update on this. My experience today wasn't great. I had to go extra gentle as part of our agreement because she didn't have the time to prep for it.
I found myself spending most of the time fingering her asshole to try to get her ready. The one time I finally managed to get the tip in, it was painful for her so I had to pull out straight away. It was a quite a waste of paying extra in the end.

I also found her a little less attractive naked so I think I wasn't really feeling 100% on it.
She had somewhat of a confident personality about her, but not such in a good way.
I didn't quite feel "relaxed" if you know what I mean.