I have a h-reg (1990) mini mayfair.

My battery goes flat on it constantly. When i recharge my battery everything
is fine, the car starts with no problems. The problems start after i've
taken him for a long journey. Once I've been on a long journey the car won't
start again afterwards due to a flat battery.

This sounds like the alternator I know but it's just had a new one. I don't
know too much about cars but i could hazard a guess that because the car
doesn't cut out when the battery is flat (it just won start), the alternator
must be fine because it is powering the spark plugs???

I've spoken to a few people, their ideas involve things such as the fan belt
slipping, (is this viable). Another person was telling me about a problem
with minis to do with the earthing cable on the battery but i couldnt quite
grasp what they were saying, (any ideas about this?).

Thanks a lot for any help you can offer me and after this has been sorted I
have another small problem to tell you about involving a clunking coming
from just beneath the mini to the rear of the front seats.

Cheers
Will.