Check out pcw_exhaustmods on instagram. He’s just off the M1 near Milton Keynes. He has quite a big waiting list I think, a good few months so definitely contact him soon if you’re interested. It takes him about an hour to do and he charged me £270 I think. Crazy cheap compared to most other options.
He’s a bit secretive on what he actually does as he’s had some copycats trying to do the same service, but from what I could tell he takes the exhaust off the car, makes small cuts to the top of the exhaust (can’t see it when it’s attached to the car). He then pulls out all the crap that’s in the backbox and cuts small holes / openings between the different compartment to increase the airflow. For me he also did something to the resonator as he said due to the OPFs, modding just the backbox might not be enough to get the pops and burbles. Then he welds the cuts and puts the exhaust back on the car and you’re good to go.
The car doesn’t pop at all under 15-20mph unfortunately as MINI coded it out but it still burbles and sounds good. After 15-20mph it sounds amazing, pops constantly but they’re quite deep pops ie it very rarely makes a sound I’d call a “bang”. Motorway drone is pretty good / non-existent except for when you put your foot down, then it gets quite bassy. But it also pops on the motorway which is fun. Cold start is probably the most annoying part of it, it’s pretty loud I have to say. But neighbours haven’t complained (yet) 😁