I have never used WYP. So what's the average rate they are wanting for coming out for drinks with?
I used it few years back and it was around 50/100. But depends on the girl and what you want. I have been asked upto 200-300 pounds for a date in a fancy restaurant but I never used that option.
For me it seemed more tough conversation. On SA, I can clearly state that I am looking for an intimate arrangement and even for casual meet I can have bit of fun(sitting closer, mild kissing, holding hand etc. there has been occasions when it got too intense just over drinks. I am lucky that we were not thrown out of the clubs

and if the girl seems too cold, I can take that as reason that there is not enough sexual chemistry to proceed for next date.
on WYP, it can be tricky as the girl would clearly state that this is platonic meet and all you may get is a date with girl. Who will eat and drink at your expenses and get more money on top.