Weather, lifestyle, age. To not move in to the back of beyond because it may sound idyllic but presents an awful lot of problems not only with weather but if you should require emergency services of any type, or shopping. Not to buy too much land, it costs to upkeep it what with fencing, tractors etc. To rent first to make sure it is what you want and where you want. Make sure the weather is going to suit you. South can be very very hot and the north not much different to the UK. Think seriously on the financial side. Not just for today but for a few years down the line. Research research research. If you go on expat forums, (excluding this one) don't believe everything you read and learn that some are best avoided. Don't buy a huge house because you can, only buy it if you need it. If you are thinking of working here, remember it will be a hell of lot more difficult. If you are going to be self employed its not only very expensive but until you have established a good reputation, which can take a couple of years, then you could be having to support yourself.
I would advise looking to be within easy reach of a town/couple of shops. Too many people take themselves off to the back of beyond and then feel trapped - they do it in the UK too! You never know when you will be unable to drive, or the car may be out of action and then you are in trouble. Also, do not take on too much house and/or land! I have lost count of the people here who have had to sell up because the land has become too much for them. In the north and west of this country grass needs cutting almost daily in summer. As one ex pat said to me "we have had to downsize here because we were having no retirement, nor were we seeing anything of the country. We are just slaves to the house and the land." That goes equally for people who are coming to work here. Another point ...... check the weather in the area if you can, particularly if you are outdoors people. In some parts it can be the equivalent to moving up north from the south in the UK.
I would ask about resources and services such as a good shopping centre within reasonable reach and also access to travel such as good roads, rail and bus services, airports and ferry terminals.
Its lovely to be in the countryside miles from anywhere but if you end up having to pay a small fortune to have utilities connected, its not so much fun. Think about moving to the edge of a village or small town to save.
24/7 in France: Preference for rural vs. city? Inland vs. coastal? Weather and seasons? The answers to these should narrow the focus, regarding what region to start from.