Ok, that's great and really helpful! But just a few more questions because, quite frankly, electricity is like witchcraft to me!
I have been and got a multimeter which I'm hoping is gonna make this a bit easier.. I know which one is B+ so that one goes to the battery/starter, the wire is pretty thick, as thick as the one on my polo if not thicker and the alternator puts out around the same power, 55amps. I intend to sort the wiring out properly at some point so for now that will hopefully be OK.
How can I find out which connection on the alternator is the excite/field terminal? I don't have a diagram and nor can I find one..
Seriously thanks for the replies, I'm really struggling with this haha