Try this list, may be a bit out of date, just phone round.
http://www.wales.nhs.uk/sites3/Documents/262/N HSDentists%20April%2008.pdf
I would say get her registered the earlier the better, my kids went from the age of about 8 weeks, but that's because I took them a long with me when I was going, I think they do recommend going from the minute their teeth appear for advice and prevention of decay information.
I am glad to say, because they were so familiar with the dentist they have always been happy to sit in the chair and have their teeth checked. They are coming up for 9 and 8 now, and luckily they have never needed any treatment yet.