Having read many articles on the heater blower being intermmitent,I had the same problem with my XM turbo diesel estate.
I had a situation where my key broke away from the remote plip,so I went to my local key cutting service and had two new keys cut.
The first thing I noticed was that the key would only fit the ignition one way only.whereas before it would work in any combination.I have also noticed that the blower heater now works and has done so for the last three weeks.
Could most of the problems with the heater be due to a worn key,or have I just been lucky? Any comments.