Double Social Security

I was wondering whether there is anybody else in the same or similar situation to me.

I'm basically "retired", receiving a German pension (mostly) with a British state pension with it. But basically since I retired, because of age, in Germany, I remain socially insured (health) in Germany. If I were sensible, I'd enjoy my retirement and pay tax and health contributions in Germany, gain access to the French health system via the E121 and have a "mutuelle" top up.

But, as a work-a-holic, and the fact that my company still needs me, I shall continue on a consultancy basis. I have been looking at all the various options on being self employed, but cannot for the life of me find out how to avoid paying double social security charges. The Germans want 18.2% of my world-wide income for health charges, the French seem to want around 25%. What is worse, is that as soon as I start earning outside Germany, the Germans will tax my pension as if I were a single person and without any allowances! (The idea is that you'll get these allowances in France)

So has anybody here been through this hoop?

I have it forthcoming, having deferred my German pension but with UK one due to start soon. I'm looking into it and find the taxation a gloomy prospect.