Brilliant.. if you get me a pic before i tried it that would be definatly useful! Thanks for you help much appreciated!
Found a pic on the net I could draw on.....
Loosen the bolt in the picture

To tighten belt, pull Alternator upwards, to loosen, push down, when the desired tension is met, tighten up the bolt again. Try not to over tension the belt, there should be some play in it, enough that you can at least twist the belt 90 degrees.