French nationality

Naturalisation          from Reg Dickens    Resident in France for 40 years
     Divorced in the UK and married to a French woman for 45 years
Following brexit and having lived in france for some 40 years , married to a french lady , I decided in july 2016 to apply for french nationality .  Fear of the unknown perhaps ?
I submitted my " file "3 times  ( always something missing ) prior to it being accepted for further processing .    Finally in August 2017 I was interviewed by the local police  . who asked for information , not at all mentioned in the original application document . some 2 months later i was summoned to the Prefecture in Caen . Where even  more  information was  requested  .
My application was accepted . including the statement that  all of  the necessary documents had been provided . and the file would be passed on to the Ministry of the Interieur . 2 months on this ministry have  requested the original of my first marriage certificate ( I was divorced 45 years ago ) and also they want a copy of my divorce " certificate " . ( I have not kept these documents from more than 45 years ago )  I doubt also that my ex wife has copies either ;. Nowhere  in the prior documentation does this request appear . I do not understand why they need this     .They have an attestation of my marriage to my present wife ( french )   and of, course the decree nisi was presented to the registry office at that time .  I really do not have a clue how to obtain copies from the Church ? or the " divorce " authorities.
Has any other divorced person in the same circumstances  encountered  the same request and difficulties with their applications?