did the battery light come on at any point?!

if the voltage when running is anything under 13 volts then chances are its the alternator or the blue wire which runs to the revcounter (if the battery light didnt come on, ill bet money on this being the problem!)

whip the alt plug off and take the dials out, test the continuety of that blue wire with a multimeter (think its blue...the thin one anywya), if its broken then just run a new wire and try it again, if its still not working then its probably the regulator thats gone, easiest thing is to go to a scrappy and get hold of one out of there, chances are they wont have scrapped a car because of a duff alternator

hth mate!