Its been covered many times so have a bit of a search for more detail, but in summary;
You can buy a car in France and bring it back here - theres no additional tax to pay.
A UK classic insurer should be able to insure it against the chassis number - a French insurer would be unlikely to offer cover if you are not resident there.
Yes, you do have to register it in the UK but its straightforward - get an MOT then toddle off to DVLA, hand them money and fill out the appropriate forms.
Personally I'd drive it back so long as it was road worthy and legal. However, a UK resident and licence holder driving a French registered car that they own, in the UK might be an interesting legal situation but the chances of you actually getting caught are incredibly small. Worth further investigation though...