I'm going through a similar issue just now Mat. My lovely dog passed away in June this year of chronic heart failure. Because her vet record from when she was a puppy stated she had a heart murmur, Animal Friends are saying the claim has been declined. Our vets have contested it on our behalf saying chronic heart failure is very different to a heart murmur as humans and animals can live with a heart murmur for years. The only signs of heart failure came in June. It's currently going back and forth between the insurers and our vets. I intend to take it to the ombudsman if not resolved.