Thank you Grumpy and yes when I read this yesterday I immediately thought of Col, the symptoms are just the same and as the condition is rare in cats I can't blame the vet for thinking Warfain poisoning.
I've joined the FB group and a couple on there suspected Earfarin but they were indoor cats. I was never convinced Col found a dead rat and didn't bring it home to show off with it. Hence us worrying it was deliberate. Col hadn't yet managed to catch anything
I'm going to phone my vets later and hopefully they are aware