My friend and I both had Xantias (N reg.) with the same problem. He replaced the switch at the bottom of the ignition barrel - problem solved. I didn't want to spend money so I used a different solution. Switch on the engine. Do not switch on any lights, wipers, or any other electrical equipment. Wait for 1 minute, then switch the blower to the first setting. It works - and it stays on. Well, mine does.
Colin Harold, April 2008