Mini Roadster Brake Issue

That sounds awfully similar to an issue I had with my Mini Cooper a while back. I also got a strange error message and the brake pedal felt like I was stepping on a brick. The error memory also had a code related to brake performance. Have you checked the vacuum lines to the brake booster? Sometimes a leak there can cause similar symptoms. It's like trying to drink through a straw with a hole in it – you're not going to get the full effect.

Interesting. I haven't checked the vacuum lines specifically, but I was wondering, did your issue also trigger the error message in the speedometer? I'm trying to narrow down if it's definitely the brake booster pressure sensor, or if there could be something else at play before I spend the money.

Yes, the error message in the speedometer definitely points to a similar problem I experienced. Given that you've already got a code pointing to the brake booster pressure sensor and you suspect incorrect bleeding, it's highly probable that's the culprit. The brake system is crucial for vehicle safety. I would suggest getting it checked out by a workshop. They will be able to diagnose it properly and make the necessary repairs.

Just wanted to let you know the problem is now sorted. Turned out it was indeed the brake booster pressure sensor playing up after incorrect bleeding of the hydraulic brakes. Cost me 90€ to get it sorted, so not too bad. Thanks for the help!