Have had the Cooper a few weeks and the good things are:

Roadholding
Space in the front

Less than good, bordering on the slighly annoying:

Engine sounds a bit rough at idle, others have detailed this and is just how it is it seems

Pedals, if you have big feet, the clutch pedal linkage will hit your right foot if on the brake (a result of confined space I assume). And the steering column bolts hit your feet on full lock

Heating, struggling to find a happy balance, it is either too hot or too cold, nae blaw or too much. The heated front window option we took is also pretty poor which means relying on the normal heating, which is not great.

Interior light pack, seemed funky at the time but not worth the money, if you are thinking of getting it, I wouldn't