If the 200cpsi cat is hot it shouldn't be too difficult to pass the less stringent emissions from 1996.
I’ve had a look and it’s a cat. We’re not going for power mods so a second cat won’t hurt if it gets it through the mot every year.I'm not sure if you need the second cat, as I think emissions are still pretty relaxed up to around 2000?
Maybe get the old centre pipe removed and first check whether it is just a resonator section or a cat and then replace it with same. Hopefully, if it's a resonator, it will save you a few quid!