I suspect this sort of referendum might not follow as predictable a pattern as other "Social issues" type stuff, as immigrant heavy big cities would have much higher anti-SSM votes than they might otherwise have; and even exurban or rural areas would probably not reject it as heavily as otherwise.
So basically
France:
Biggest Yes - Paris Intramuros/Hauts-de-Seine/Yvelines, most of the big citiy municipalities and then the usual suspects like Brittany
Biggest No - Seine-Saint-Denis and other Banlieues, follwed by the Catholic
UK
Biggest Yes - parts of London, the University towns, Scotland
Biggest No - places like Bradford, Oldham, Blackburn...
Germany
Similar pattern to the above, but maybe an East-West divide too?
Switzerland
Something like the inverse of this, French "protestant" (ie secular) cantons and cities against Catholics and rural Germans