Hi, welcome to the fold.
I'm sure many of us here have done exactly what you have done - bought a 406 as a stop gap/run around/ bargain car with little or no expectations, but found it an absolute joy to own, a very underrated car, and hung on to it..!
I've had a few 406 estates, all diesels and the latter two were 2.2hdi models that were 'tweaked' a little - resulting in a practical, reliable and comfortable car that was a bit of a sleeper...
Enjoy the car, feel free to have a look through the Knowledge Base on the home page for guidance if you have any issues - but you can always post something up if you need help, sympathy or simple moral support
As a side, if you add your location to your signature, maybe a member local to you could help out with diagnostic work etc, should the need arise.