Alfie156,
i had today the same problem

I have noticed it last year, it happens mostly when its cold and wet. You have to turn on and off the light ~30 times and it works again.
Ive heard from other alfisti here that they had to replace the whole unit to get rid of the prob. as usualy alfa doesnt want to know about crap they sold to the people. One guy told me to refix the welding contacts. But you need a flex-plastic arm to get to the xenons if you dont want to dismantle the front
cheers
selcuk