You'll be OK if you are of state retirement age as you will be able to join the French health care system using a form S1.
http://www.nhs.uk/NHSEngland/Healthcare ... broad.aspx
Basically the UK will pay the French authorities for your care.
If you are not in receipt of a state pension and not working then it's much more difficult . You can get cover from the UK (again using an S1, form 106) but it only lasts for 'up to' 2.5 years. The length of time depends on your contribution record and the time of year you apply. After that you cannot join the French health care system until you have been legally in France for 5 years.(and gain the status of a permanent resident). During this time you have to have health care to be legal and therefore have to have private insurance with very comprehensive coverage. For someone who has a pre existing condition this can be very expensive and in some cases unobtainable. You also need to make sure that you fill in French Tax forms each year to be 'legal',
If you have been here for 5 years and still haven't a UK state pension, then you will have to pay 8% of your taxed income above a threshold (around 10,000 euros) for healthcare.
(this all may change again, the rules have changed since we came here 11 years ago to what they are now. I believe that there is a challenge to the new rules at EU level but I have also read on a French forum that people are having difficulty in some areas getting into the system even after the 5 years are up )
The most important thing is to make sure that you don't try to 'wing' it. I've heard of too many people who have ended up with crippling bills .
Once in the French system, health care is good. Diabetes, both T1 and T2 (on meds) are reimbursed at 100%, which means that almost all your diabetes related costs are almost totally covered, as long as you go to a doctor that charges 'agreed' rates for consultations.
When you visit a doctor, you may have to pay upfront but will be reimbursed directly to your bank account. At the pharmacie you don't tend to pay upfront, it's all done directly(the authorities take any money owed out of what they owe you)
For non diabetes care, you will get get reimbursed usually at 65-70% , sometimes less.(depends on what it is)
These costs continue even for those with a state pension
Some/most people obtain 'top up' insurance to pay the difference.
I think that most people with T2 are treated by they GP. however you can ask be referred to a specialist or even just choose one and make an appointment (you'll get lower reimbursement for that) . Most of the drugs are the same, sometimes from different manufacturers, generics are substituted by the pharmacie unless the doctor writes non substitutable on the prescription.
Type 2s no longer get testing strips reimbursed freely .There is a maximum of 200 a year (although I think that more can be prescribed by a specialist in the context of education) You can get a new meter prescribed every 4 years; they cost a lot more here than in the UK.