wrinx,the old mini was a pre-engaged starter,it doesnt work on modern cars, if it does it get a jump lead and put it on the negative battery pole and connect the other end to the engine somewhere, that will tell you if the earth is broken.
If its happened once it will happen again. It sounds like a 'dead' spot on your starter motor. The next time you hit thisdead spot you will get the same problem. The motor is also likely to get worse and more dead spots will appear. It may last for another 6 months or even more but can you take the risk of being stuck away from home one day?
I think you shouild look into getting a new starter motor soon...
Mine had a dodgy starter motor sometimes playing dead. The problem was the solenoid that engages the starter also swithces the power like a big relay, the meahanism gets gummed with dried grease gunk and stops moving. Clean it up re lubricate it and clean up the contacts while you're there. should work fine. But try to get the ***** out on a V6