Yeah it is looking like the cat at fault. Had an intermittent lambda error coming up for ages, stupidly just replaced it now so that's sorted but the emissions are still up. Car is still runs very well, no signs of anything else at all so the garage is recommending the cat goes. It's SWR in Stirling that I'm using, so I definitely trust what they're saying.
Forgot to mention that the car was definitely running rich, so that's probably what's goosed the cat
but but but the magic k-tec rolling road says "+5bhp"