If he owns property in France, he must make a French will. If he rents his French home, and his whole remaining estate is based in England, he must make a UK will. It sounds to me as if he may be suffering the early signs of dementia, and these signs are worrying him. This is exactly what happened with my own father. He tried to fight off the forgetfulness, and this made him aggressive. Unfortunately, if it is dementia, your father will forget what he said to you, and will probably become even more aggressive if you try to remind him. This may be the moment for all his offspring to get together to persuade him to give you ( some or all of you) power of attorney. Taking control of the affairs of someone who will not give POA, and who is now clearly demented, is a nightmare in the UK. I dread to think what you would face if you had to do such a thing in France.
My sympathies are with you