Pippa, there has been a lot of discussion on here about Equine Dentists and if you go a few pages back you will find it. Suffice it to say that the recommended equine dentists are listed on the BEVA website:
http://www.beva.org.uk/taxonomy/term/100
If you want more information, look at the entry under Equine Health Matters on the left hand menu here on NFED.
By the way, we are not able to recommend anyone who doesn't advertise on the NFED Directory, as the advertisers fund the site.
http://nfstallions.info
http://forestuprising.org.uk