It has been done here in the U.S. for quite awhile now but the warranties usually come with some terms and conditions. For example, one of our five had a two year warranty that required the Orthopedic Foundation for Animals (OFA) had to confirm the diagnosis at the owners expense and that if environmental factors were determined to have led to the HD or ED, no refund was given. This breeder also required that the dog be returned and euthanized to avoid its suffering in order to receive a full refund. That's an extreme warranty, but they do exist. (This was not our Angus's breeder.) Many U.S. breeders are now including the OFA confirmation be done because there is a high rate of false diagnosis from Vets who are not experienced in the correct way to take the X-rays and most do include the exclusion of returned payment if the owner's environment caused the HD/ED....as I wrote above, Breeders can only do so much when there is no genetic test to rule out HD, so no way to only breed dogs who don't carry a gene that causes it.
I remember a thread a while back where someone said their insurance did not cover HD (not sure about ED) because of the fact that there was such a heavy emphasis on the environmental factors - it almost sounded like was wholely laying the blame at the feet of the owner. I don't think that is at all usual, and no idea who the insurer was - UK or otherwise.
Insurance has only recently arrived in Andorra (within the last few months) and it has exclusions for HD and ED, as well as cruciate problems. And pretty much everything else that is likely for Labradors. I declined.
I am pleased to hear another owner refusing/delaying surgery. When ours was diagnosed with HD at 7 months and ED a few months later I was told that he might need surgery and that I could expect significant arthritis to set in by 3-4 yrs of age. In fact, I declined surgery on his elbows when told that the success rate was 60%; so there was a 40% chance that it would not improve, or could be worse. We decided to go the nutriceutical route and use pain relief only on those few occasions when it was obvious that he had overdone things. He had a full and active life, and his slight limp never did get any worse, nor did he go on to develop the arthritis, so I do not believe that the operation would have contributed positively to his well-being in the long term, and would have been detrimental in the short term. Don't get me wrong I would not have let him suffer, and all cases are different, but I do think that some vets see the diagnosis as a call to action when just waiting and watching may be a good idea.