I messaged Notaires De France ,asking if my sister, who is a co-heir and has been inhabiting the family house for the last six and a half years, if it was legal. Apparently it isn’t and she would have to have my permission and a legal document to permit this.
There is a French will.
Anyone come across this?
Not personally, and I sympathise with your difficulties, but is there really a need for another thread since you have already asked this (and had some suggestions) here?
https://www.survivefrance.com/t/an-honest-notaire-in-vaucluse-recommendation
This specific question was not answered and a forum member advised me to open another thread for specific questions. At least I’m not deviating … lol
Similar to when OH died, the family car carte grise was in his name but the children had to get an attestation and sign it from our notaire allowing me to change the paperwork into my name and be sole owner of the vehicle. Everything to do with the sucession had to be agreed, attested and signed by all of us.
and Notaires de France only gave you a very general reply and admitted they could not give legal advice. They advised you to contact a Notaire.
From your other thread, I think it’s obvious that none of us who have replied (so far) have experienced a situation as complicated as yours.
All we (and you) can do is rummage through French legal websites and grab hopefully at paragraphs of this and that… which can lead us all a merry dance.
I think it will take a French legal eagle to properly understand and unravel your situation and you will need to be onhand.
Best of luck.
I too sympathise @SallyD , as I am in a not similar but nevertheless frustrating inheritance issue, but it does no good to start another thread.
This is because if someone does have a brainwave of a solution they can end up in the wrong place to post it and others might miss it altogether.
Thread drift can be irritating but you can drag it back to the point any time you like so that you miss nothing.
Fortunately in my case, I can walk away from it and say stuff the lot of you. 
I think. 
Time to take the services of an avocat. It will not be free but it will be money well spent.
The other thread seems to have established that there is an apparently straightforward legal process designed to oblige a co heir to formally accept or partially accept or refuse the succession within 2 months of being served with the injunction. The injunction can be served by a huissier. Huissiers are normally less costly than notaires or avocats. I imagine this could be done online from the UK quite easily.although the OP would be well advised to employ a human translator I think.