HJS cats could be an option, I have these on my current car and a set similar to these on my previous car. They always pass MOT emissions.
HJS Tuning-Katalysator 90 95 0092, bis 240 PS, bis 2600 ccm
https://www.hjs-motorsport.de/produc...catalysts.html
I paid around £340 each.
I got paid £125 each for scrapping the old cats.
They can work without ECU coding with these angled spark plug anti foulers. They take the rear O2 sensors out of the direct exhaust flow enough to trick them not to trigger the engine light. All that happened on the previous car is an occasional fault code about implausable O2 readings.
https://www.privatelabelmfg.com/prod...-fix-angle.htm