Electrics, well they are multiplexed, as will be your 406, so nothing really added in there. Most of the time if there is a problem it is down to the multiplexed comms2000 unit and that is very easy to change and not too costly, should it go south!
Ive heard of very very few C5s having trouble with the main BSi brain, as it is usually something to do with the above.
In the 3 years and over 100K miles collectively ive only ever experienced a few minor problems with C5 electrics. The worst one being the indicator would flash and then turn off while putting on the headlights. This was a comms2000 fault, I decided to buy a new unit for £180 but they are available used for much much less and it only took me 20 minutes to change as since that C5 did not have ESP or H3+ (I doubt you will find a 2.0HDi 8v with ESP and you wont get one with H3+) the unit did not need coding in to the car.
The only other problem would be the climate control can blow hot one side and cold the other, though there is a fix for this, again its simple and not costly.
What is the worst you could happen?
You could always sell it on should it do something unheard of, though I doubt you any serious electrical issues. Having a Lexia might be a bonus, though you might not have to use it. I bought one due to curiosity, not because I needed to use it We have had three 2.0HDi 8vs and all have been excellent cars, no real problems and I would like to keep our current one for much longer as its such a good and reliable car.
Im sure they would fit your needs very well, as they do actuall have some advantages over an XM, and it should prove to be a reliable car. I know a many people who have been C5 converts and run one after the other now with no serious faults. Many are used as Taxis and often get retired at around 300-350K. The Taxi driver who I spoke to had a fleet of 8 and said he would not run them if they cost him time and money.
Im sure you will enjoy one
