Sorry to hear that Stephen, if it is the cats that are damaged and not any of the lambda's it would make sense for the difference in cost to go for the Supersprint.
The system is good to go, all sensor fittings are there and the ECU adapts well with fuelling. Had it checked, idle/cruising is at stoich, runs rich on wot at the top end which could be normal anyway for the GTA engine... though I am after some opinions on that preferably from someone not trying to sell me a remap
Think I'd be correct in saying that as it's Euro III the last two sensors after the cats are there to monitor the efficiency of them, remove the cats altogether and the MCF message will come up. Question is, with a custom made exhaust if you can remove the main cats while having just the warm up cats on their own, if they would be enough for these sensors, afaik they cannot be mapped out.
In 7,000 miles with full system only had a message come up once, not really counting it either because I'm certain it was dirty fuel, needed to fill up off the beaten track driving through Belgium once as I was on vapours, diag read cat below efficiency threshold. Have never had a problem on UK 95-99, worth mentioning still if fuel quality could be an issue.