Mid journey home tonight I got the warning "bing" followed by amber messages in my MFD "hand brake system failure" and "hill-hold system failure", whilst going up a small hump (overpass for metro station). An amber "!" in a triangle then appeared at the bottom of the dash and stayed there the whole journey. Luckily the rest of my journey is relatively flat. Start-stop stoppages didn't reset the system.
Once home I turned the ignition off and back on again and the fault was gone. Had a quick drive around the block and I was satisfied it was working correctly. Something to keep an eye out for.