Hi Roy
Thanks for that photo, it shows that the handle hole in your inner door skin is much larger than the holes on both my doors. Where the door pull bolts attach on mine is behind the inner door skin and the bolts go through holes in the skin. It explains my problem. They must have tried a different style of inner skin at some point in 1983.
Although the posting topic is Passenger side electric window, this will probably apply to both sides, and the photos here are of the drivers side.
This update is for all Murena owners as I have just been doing a demonstration at the recent Practical Classics Restoration Show and replacing a window motor just afterwards, which has refreshed my memory on this subject and I can now see that it appears there are three possible installations at least, that Matra probably made when installing electric windows! (or maybe converting a manual one to electric)
The first photo shows the larger opening on the door panel and crucially the door handle bracket having a support bracket fastened on the outside of the panel and riveted there, with the mechanism trapped inside the door handle bracket!
The second one shows the later smaller opening, and the mechanism is still inside the door handle bracket, but this time the front support is not riveted and the bracket is behind the panel so although it appears to be trapping the mechanism in there, I believe you can flex it inwards to leave a gap such that the mechanism can be removed. I admit though I haven't done a swap on one with that assembly.
The third photo shows the later small opening with the mechanism just visible passing behind the door handle bracket, which makes it much easier to remove the motor and mechanism assembly.
So I apologise for suggesting you don't need to drill out any rivets because it appears that in the first case at least, that door handle support bracket would need to be released to allow the mechanism removal.
Roy