Following on from the comments on Delightful Dentistry I thought a few words about dental hospitals might be a good idea.
I was being seen by an NHS dentist (and very fortunate to be able to find one!) in a standard dental practice. I was referred to the dental hospital because of the complications of EDS. However, anyone can attend a dental hospital and receive emergency treatment free of charge. As I understand the situation some dental hospitals run standard dental service clinics, particularly for children, but they are probably tricky to find.
To be referred to a dental hospital if you have special needs is straightforward. The nearest dental hospital will be based at the nearest large university which has a medical and dental school attached to it. A GP can refer you, or your consultant. I suspect for those who need to see a specialist dentist for medical needs that a phone call to the dental hospital will give you the information you'd need about which particular specialist to see and how to be referred to them.
The treatment at a dental hospital is provided free at point of delivery by the NHS just like any other hospital service. It's worth traveling for, even if you have to travel a fair distance as they have the facilities to tailor the care to individual needs.
Google list of dental hospitals (there are probably more if you put in tailored search terms)