Largely what Bill said

also it was an alloy engine in a world of Iron motors, so the norm then was to run water in the summer and antifreeze in the winter... fine in an iron motor but in a nice alloy block what happens is that the alloy furs up and clogs the radiator. Of course it's not the owners fault that he ignored the handbook and broke his car, it's the fault of the designer and "they're always overheating, it's the way they're made"

We've had an Imp Sport sat at 65mph all the way to London and back in the middle of a hot summer with no overheating probs (and a thirty year old, standard, cooling system!!) ok once you pushed to 70 - 75 the needle started to climb but what do you expect without sorting it out at least back to factory?
As to the geniuses that claim they need extra weight in the front to make them handle/stop them doing wheelies(

) you can put them in the same camp as all the blokes that used to own a FS1E / Bantam that would "crack 110mph easy"....
IMHO the Imp had/has more ultimate grip, but the Mini is *way* easier to control at/over the limit. For the average driver the Mini was probably better, but the Imp had/has a better engine (and for a non-average driver go look up the exploits of the Imp Clubs Hon Chairwoman, Rosemary Smith. A pensioner now and still faster than 99.9% of the club at Knockhill the other year
