This is what my dentist warned me about. It's not the uk dentist being mean. They refuse because they have no idea about the underlying quality of the work or materials. So won't touch it in case it gets worse and they get implicated in the failure and could become part of a malpractice.
I was tempted but then had a couple done in Hove. My biggest fear was it going wrong down further down the track. Its hard to know what standards are being adhered to in other countries. If something goes badly wrong britosh dentists are unlikely to step in.
I ended up just swallowing the cost...