Hmm.

If you make a booking without being logged in (say in Lufthansa.de) at the end of the selection of the flights there are two possibilities:

- Login as a M&M member or
- make a manual login, where you have to state the country of residence.

When taking the second option, after putting in France:
"Vous avez changé de domicile depuis votre dernière sélection. Veuillez recommencer votre recherche."
You can put in a fake country of residence, but then later in the template this fake country cannot be changed to France.
(BTW: I checked several other countries, and the message is always in English
"You have changed to a different domicile than the one you had selected previously. Please submit your search again."
and start all over)

There are two possibilities I see:
As a M&M member with a French address you have to do your booking in French. The only possibility to go around that is to make a booking when not being logged in, typing all your details in including an address outside of France.

Oliver2002: I guess Mick and I are using a completely different Lufthansa booking system then you do, therefore our experiences are not comparable.