While I agree with most of what you've said, I am aware that many people keep UK reg cars in many EU countries for long periods without problems with the authorities. However the bit about the insurance companies not helping is not really true, as all insurance policies issued in the EU (including UK) are valid throughout the EU without limitation (check the back of any insurance cert) However the problem is that the cover is usually for the minimum in the country concerned, she naturally wants to have more than minimum cover. Thanks anyway for your input.
Edited to add- After a bit of checking the regs appear to say "A vehicle may only be used within France for 6 months in 12" Periods where the vehicle is not "in use" do not count toward the 6 month limitation.
Circumstances alters cases!!