I have also had the dreaded VDC/Hill holder alarm, I fixed it myself and thought Id mention how.
Firstly, I established what sensor was at fault, it could be the clutch or the brake, or an ABS sensor. If you try and start the car with either the brake or the clutch depressed and it wont start, then that is the faulty switch, for me it was the brake.
Remove switch, get your head right up behind the pedals, remove plug, switch comes out by rotating it 90 degrees. Spray liberally with switch cleaner, press and twist plunger to work cleaner in.
Put switch back in, spend 70 GBP (Alfa Dealer quote for parts only) on fuel instead.
Hope this helps anyone.