I first new about the 406 at my previous job because suddenly they were replacing the 405 model thst reps were using to visit clients.
Before I left (office closed) I had the opportunity to drive one, which became quite a routine driving to Torquay and Plymouth in style (well it was then!). The one thing I liked at the time was the impressive way it took off at traffic lights!
I bought my 406 just over 5 years ago, it was used and had been a reps car in the south east somewhere, but with less than 80000 miles on the clock - bargain at £2995 (or so I thought before the radiator had to be replaced not long after buying it). The standard model has a 1.9 litre turbo diesel engine and is the best one Peugeot manufactured at the time. This engine is also used in Citroen models.
It is a very safe car and it can still reach dizzy heights on the motorway although I tend to drive pretty much to speed limits whenever possible. It doesn't like going excessively slow as like most cars it will start to overheat.
I've been thinking of selling it for the last year or so, but I can't bring myself to do it as it still gets 30+ mpg normal driving and about 36-39 on motorways.
I know this model has been superceded, but if you can find one it may be worth your while. My car is now 13 years old and still no rust!
Parts I have had to replace are the radiator (mentioned above), housing for the twin radiator fans (due to another road user - I have not had an accident in the car) and routine items - tyres and exhaust. I didn't even have to replace the gloplugs til a few months ago.