The situation has changed in recent years.
For a period 2007-15 the French made all
early retirees have private healthcare insurance until they were granted permanent citizen status after 5 years. Then they were allowed to join the system by paying an annual percentage of income .
The EU found this illegal and put pressure on the French. It's
almost back to the previous system ie that you can pay contributions to belong to the system as long as you are legally resident. (this used to be about 8%) .
https://www.french-property.com/gui...s/health/getting-health-cover/early-retirees/ (read it very carefully as the situation is a bit ambiguous, it was the most recent I could find but it's worth searching for as much
recent info as you can find)
When in the system you have to go through a lot of paper work every year to prove you are still eligible. It is very important to fill in French tax return, even if you are not liable for tax in France. The form showing how much tax you are liable for (if any) is what demonstrates that you are living legally in France and is also what they use to calculate your contributions for health care.
Once in the system, your doctor should apply for you to be covered at 100% for your Type 1. This also covers things such as retinopathy checks and other conditions related to diabetes. You will still have to pay around 30% for any non diabetic related conditions and if hospitalised a board and lodging contribution. In big towns and cities some doctors and consultants also charge far more than the state system reimburses(not so in the sticks where I live) Most people pay for a top-up insurance to cover the extra costs ( although some people don't buy it, I wouldn't risk being without)
When you become eligible for a British State pension it becomes so much easier . After filling in the correct forms from the DWP they give you another form to take to the local CPAM and you no longer have to pay contributions and no more renewing every year. From then on Britain pays the cost of your healthcare although not 100%; you only get what the French will get so still need a 'top-up' insurance.
We do not know what Brexit will mean. I probably won't still be there but I am hoping that those that have permanent residence will be OK .However, I know from past experience that the French don't always play by the rules (see above). We spent a very uncomfortable year back in 2006 when it seemed that they were going to throw out those of us already in the system (and paying contributions). There was a concerted campaign and probably more importantly the intervention of various MPs and MEPs and a very last minute change of mind (though not for newcomers)