Have you tried Frynwy, on the North Wales Shropshire border http://www.fyrnwy.co.uk/ couldnt recommend them highly enough, I have used them from horses with broken jaw to hernia's, they are just the best. But i think you have to be referd there by your own vet, but because i have got horses who like to cause themselves injury or just natural issue's that arise I can now just call them up for an appointment!
It depends where in north wales you are but liverpool university philip leverhulme equine hospital will take 2nd opinion / referrals and will be much better than normal vets.
Ask your vet to refer you, they cannot refuse.
I personally wouldnt use Fyrnwy, was told by them my mare was in foal and she wasnt and a friend is also having problems with them.