If I didn't think that was your issue, I wouldn't have said so. A bad ignition switch has manifested itself in all sort of electrical gremlins.
The UK alarm system is completely different than the US model, and I could of course be wrong, but I believe the two are connected.
But, the ignition switch is an inexpensive part ($12-$20 USD) and not difficult to replace, so that's where I'd start. The Ignition switch part number is 4A0.905.849.B available from either Porsche or Audi, and there's also an inexpensive generic made by Meyle (Mfr. for Porsche/Audi), same PN#.