MY cat has had a little rattle for a while now.
Back in December sometime I was quoted over

 

Some techno-bods on here might understand why there is a difference on a Jap import, could quite easily be the case, with their higher Octane fuel, greater compression engines perhaps the CAT's can be different & perhaps our fuel over here isn't 'good' enough for Jap cats!??

 

bert_smith.. check out some breakers.. you might have to spend some time looking but I am sure you could source the part within the UK.
http://www.buy2repair.com/ have a complete car, maybe they might consider breaking it for you..

 

The cat flanges are certainly the same for UK vrs JDM, but the cat itself might have different internals. Since EU emissions are tighter than JDM, if there's any difference then it would be the UK/EU cat that would be more restrictive. Based off those assumptions (I doubt there's any difference, but there's no evidence either way!) you'd probably be fine with any S2000 cat from a scrappy.

-Brian.