Hi all I’m looking to remove my catalytic converter in my multipla to either give it a good clean or replace it, if anyone would be able to give me some instructions then that would be very much appreciated. Many thanks Fab.

Have a look at on line part suppliers. See what it looks like. Decide if it's the sort of job you can do yourself.
Possibly have a look for used one too.
I have no idea how you would attempt to clean one!