Having scoured this AO Forum about this error I have finally made some progress!
Problem: ABS/VDC warning activating randomly when driving along
1) New MIDI fuse - got this from local scrapper (Rover 75's also use these fuses if there's a shortage of Alfas) - MADE LITTLE DIFFERENCE
2) Battery Checked - 13V switched off, 13.8V when running - BATTERY GOOD
3) New Brake Light Switch - switch replaced with new one - MADE NO DIFFERENCE
4) Spraying all connections with contact cleaner and emery clothing earths - MADE NO DIFFERENCE
Two situations helped me sort the problem:
a) Girlfriend followed me home one night and told me all my braking lights were on permanently
b) Drive in dark showed that rear brake lights flickered going over every bump in the road
These lead me to think about the length of the "plunger" on the brake light switch.
SO (with Heath Robinson head attached) I put the end of a ballpoint pen (the bit that normally gets chewed) over the plunger the making plunger 1/4" longer and HEY PRESTO no more annoying beeps every time I drive.
Hope this helps anyone else in the same boat and it costs next to b*gg*r all too so worth a try as soon as the problem rears its head