I have just done this as reached retirement age in April. Since I am extremely reliant on the health system I was reluctant too. I’ll try to link my post, as in the end HMRC told CPAM before I got round to it.
However it all worked very well!
Main steps are to phone DWP to get the S1.
Get email with link to download S1
Send the S1s to your CPAM (and saving a copy)
Get letter from CPAM asking fir copy of ID and a RIB in your name
Send these in
Update your CV in nearest terminal
Done
Much to my surprise at no point did my CV stop working, even tho’ I got a letter saying it had been cancelled.
Here is link to other topic