Thanks for your replies ladies ( and now Brian ).
I've just spoken to my SIL and Rufus has been to the vet - he checked out OK and has been given a cortisone injection and a Cone Of Shame to stop him licking himself. Jacqui, my SIL, is not looking forward to explaining to Rufus that he's not allowed out and has a special outfit to wear for the next 5 days.
She even offered to come and cut Ada's claws if I popped back to the UK to fit the collar myself.
I'll be buying shares in Elastoplast this evening - they are due a large order in the near future.
I couldn't find anything at all via Google to suggest that Valerian would cause that sort of problem, in fact I couldn't see anything suggesting that it caused any sort of problem with cats, but it was one of the things that he had recently had access to for the first time and so I wondered if that could be the cause. In the meantime, I've been told that Rufus, who is/was a big bruiser of a cat is being challenged territory-wise even in his own garden- so there could be a stress related element to the over grooming.
Brian - I guess that Rufus won't be getting any more valerian toys for the time being. My 2 love them* and have never shown any sort of issue, nor my mum's cat or my brother/SIL's 2 other cats, so I doubt that they were the cause of the problem.
* I got an order sent through recently and left a sealed bag with 2 Bunny Bits (
http://www.shop.happyhousecats.co.uk/in ... cts_id=129 ) on the kitchen table and Ada thoughtfully spared me the job of opening it and giving her one of the toys
- she was in heaven with it.