Probably your best approach is to do a search on Adultwork with Hatfield as the area. Once you've found profiles that look good, copy the profile number from the Adultwork URL and paste it in to the search box here.
That will bring up any reviews or references to the WG on this site, and that way you can get a good idea of whether she's worth booking.
You can also search here for her name, or just search here for Hatfield and see what comes up.