Speaking to Brian is good advice as he has imported a few although he does own a car transporter so doesn't need to drive them back.
That said, insurance is very difficult - I tried to do it a couple of years ago and its near impossible. Very few insurance companies will even entertain the idea of insuring a UK resident / licence holder driving a French registered car that they own, in France.
Once you get back to the UK several will insure it against the chassis number for the purposes of driving port of entry > MOT test. Realistically, its far easier to bring one in on a trailer / transporter although does obviously cost more. I spent a very, very long time speaking to companies when I tried to do it, all to no avail.
Don't forget you need a customs agent to handle the paperwork these days as well.