A couple of years ago I lost my virginity to a WG. I booked an hour with an EE girl, she was attractive and I was lucky in that in a low cost EE flat with no feedback I found a girl who gave a good service and was both sexy and pleasant.
However, leading up to this I had several unsuccesful attempted punts with a number of providers. 2 of these girls were fairly terrible, no niceties just get undressed and reach for your cock. This coupled with the fact that the punting thing is quite intimidating when you start out meant I was very nervous and couldn't get hard. I finally solved this with erection drugs which I now don't need.
My advice would be pick a girl with good feedback, make sure you have plenty of time and are in a good state of mind. In my experience, Liverpool is terrible for WGs and Manchester has far better pickings.