Catalytic nightmare

As I imagine you already know, the much-feared catalyst is giving me problems.
At the moment it is just a very annoying metallic noise.
It is quite difficult to find a second-hand one in Spain (and the few that exist are around €200-250)
Has anyone drained the catalytic converter and if so, have they had problems with the MOT?

This is the Cat I bought last year. No problems with the MOT afterwards https://www.mgfntfbitz.co.uk/shop/catalytic-converter-bent-cat/

I would swear it is not compatible with the 97 mk1

You are right because I assumed you had a Mk2 F.  It could be useful adding a note of your car to your signature, then we will know..

This one is correct for you https://www.mgfntfbitz.co.uk/shop/catalytic-converter-straight-cat-mgf-mk1-mgf-trophy/