firstly welcome potto and i hope you join the club!!!
i believe the water pump is driven from the crank, yes im sure it is, when i replaced the thermostat its seems like it comes off that, and yes its an electric fan on the bis, keep it toped up with water, the first thing i can recomend with purchaseing a bis is to replace the thermostat. This is where the fata flaw of the BIS is, in its cooling system.
I did loads of research a while back and found that the thermostat is too far away from the engine head, so its in a cooler location so opens much later, between 84 - 89 c i think, or somthing like that. I have found a garage which converts the thermostat over to the head so opens much earlier,. the other option is to buy a thermostat designed for a hot country so opens much earlier, or altrenatively remove the thermostat so the engine is alwats cooled. However this mean the engine doesnt warm properly. look out for light brown thick oil, keep the water toped up with 50% antifreeze with corrosion inhibitor, (aluminium engine' corrode very easily) must do this myself!!!.
This is the knowledge my brother passwed onto me a while ago, i hope it helps, im sure most of you know all this already and know much more but i believe its good advice!
i will be setting a date for the runnymede bbq meet this week so keep an eye out everyone. :wink:
Chris