When i brought my car because it was 120hp ( what ever that means) i was unable to get insurance out under my own name untill i turned 25. Not 1 insurance company would even quote me.
The only option i had was to insure the car in my mum's name and i went on as a named driver. ( makes no sense to me that they would allow me to be a named driver but not have my own insurance)
Since the car is registered in my name i was told that i would have to get my mum named as the registered owner, but they still went ahead and insured. I was told if either of us were to claim on the insurance then they MIGHT refuse to pay out if the car was still registered in my name. There was never any follow up on this. This was 3 years ago!
To this day the car is still registered in my name, and i'm still only a named driver. Mainly because after so many years of only being a named driver when i went to renew the policy 7 months after i turned 25 the policy was 3 times the orginal amount, i was told this was because i had not had insurance in my own name for the past 2 years.
Each renewal I check the price for myself as main driver and i can never afford it so we just renew my mum as main driver and me as a named driver.
I asked last renewal about if we needed to claim and the car still being registered in my name and was told that a 3rd party claim would be issued but again if a claim was made for my own car it MIGHT not be paid out.
Also about him getting insurance out as well as you having an insurance policy, you cant have 2 people insured on the car as main drivers. I was going to get a policy out on a banger ( a friends car ) just for a year to have at least 1 years no claim bonus and was told that you cannot do this. Even an open policy doesn't allow this, there is always 1 main driver and then anyone over 25 with a full licence that has your permission can drive the car.
Since you are renewing and there is not going to be a gap in your policy i dont see how he could get an insurance policy on the car, even if it is a "family" car. If he did it would be void. If you having been paying the insurance, tax, petrol or even repayments of the car yourself, i.e not from a joint account, can it still be classed as a shared car since you have been paying for everything? If this is the case.
I would send a registered letter or a letter from your solicitor, so you have solid proof that you have informed him that even if he does take out a policy he wont be covered, and that you will not be adding him as a named driver.
For an example if you still have repayments on the car, and the finance is in your name and he has taken the car you, you are still responsible for making those repayments regardless who has the car, since the payments are in your name. Thats the law. Reporting it as stolen and for it to be classed as stolen because the car doesnt belong to him, i think would mostly come down to who took out the finance and making the repayments or who purchased the car. If the car was purchased together then you might have problems it being classed as stolen and the guards will say it is a civil matter and say there is nothing that they can do.