Most 406 saloons were snapped up by taxi and minicab firms, and by businesses for their corporate car fleet (something on the order of 60%, I seem to recall).
My own saloon was previously owned by Britannia Insurance down in Glasgow, where the registered keeper basically only ever drove her to and from work. 27,000 miles over a 9 year period.
I wonder what Britannia's current corporate car fleet consists of now, and if they think they're any better than the 406...
2002 (D9) Peugeot 406 Coupe SE, 2.2 litre Petrol. Scarlet Red/Rouge Ecarlate/Rosso Scarlatto. Black Leather interior. SOLD
2008 (E60 LCI) BMW 525i M-Sport, 3.0 litre Petrol. Carbonschwarz Metallic. Black Dakota Leather and Myrtlewood interior.
Guess the late reg just means it didn't sell straight away, (my last car was a July 99 'T' reg Xsara HDi 90 - this one only has to have been registered 2 weeks after that).
2002 HDi 2.2 Exec Estate, (2008-12) (wonderful)
2003 HDi 2.2 6-speed Exec Estate (2012-19) (also a gem)
2009 Citroen C5 2.0 HDi VTR+ Estate (godawful heap)
2008 BMW E91 330i touring (great fun - murdered by a reversing SUV)
2007 BMW E91 325i touring (slower smoother quieter)
I dont understand your numberplate scheme, although it seems more logical than the mess we have over here in NI, but i like my English reg i was offered the chance to change it to a NI reg i said i like it, its got USB in it bound to be worth something to fans of Flash Data Storage Devices (not me). But ROI has a very organised reg system it shows both the year and where its from
English plates started out like that, with the first part giving a location and letter at the end giving year, but it all got a bit silly with people wanting to have 12 months of "Look at me I've bought a new car" and nobody wanted to be busy with that coming up to Christmas & the New Year, so they changed it to August. I think by the time the year letter was at the other end of the plate the location had gone out of the window too, although I think they resurrected it with the latest version.