Mini Clubman Engine Troubles

Rough running and stalling definitely point to ignition issues. I had similar symptoms with my old Volkswagen when a spark plug wire was loose. Have you checked the coil pack connections and spark plug cables? A faulty connection can cause those problems.

I haven't looked closely at the connections. When you say "coil pack connections", what exactly am I checking for?

I'd start with the basics. Make sure the coil pack is securely mounted and the connectors are clean and tight. Look for any signs of damage to the cables themselves. Given the symptoms, it really sounds like your ignition system. If you aren't comfortable doing that, you might want to get a professional to check it out.

Just wanted to update you. Took the Clubman to a mechanic. Vehicle diagnostics confirmed it was a defective ignition coil, just like you thought. They replaced it, and it cost me 95€. Runs like new now. Thanks for the help!