I don’t have access to a birth certificate - what are my options?

I have been working as a micro-entrepreneur for over a year now and have been paying all the taxes and social contributions mandated by law - however, I am still on a temporary numero de securite sociale.

I believe this is due to the lack of a valid birth certificate. I have entered France as a naturalised UK citizen and I have provided both my passport and certificate of naturalisation. However, I am not a citizen of the country of my birth (the USSR) and as such I am unable to request a birth certificate from the country of my birth as they require proof of citizenship before processing such applications.  I have written a letter explaining this to CPAM which remains unanswered so far.

I am sure that my case is not unique - there must other people who arrive in France without a valid birth certificate… do you know what laws/options apply in such a situation? would I remain with a temporary social security number indefinitely? I notice that a birth certificate is also a requirement for a French driving license, which I shall need when my UK license expires in a few years’ time - so a similar issue is to be expected down the line.

Thank you for any advice you might be able to provide.