you have to read the policy very very very care fully, most policys assume you own the car and do not ask who the owner is, but state in the policy the driver mustbe the owner.
Most will not touch you if you are not the cars owner.
if you are oging to do that route, you could do what the indian family do in my estate they have a banger that they keep just road worthy its worth like £20, they only insure it for 1000 miles a year (the insurance want proof of it in the form of copies of the MOT Cert)they insure it to the youngest in the family, and it dosnt move the take it out for a 5 minute run evry now nd a gain, and have a stupide excess on it so its only a couple of hunderd quid to insure, mean while the person is named on another policy but declare they have their own car etc so. the system works quite well.
but that was before the insurance started doing named get NCB.