When you are stop-checked by the Police, they can complete checks on their databases to make sure that you have a licence, insurance and MOT for the vehicle. Technically it is an offence not to change your address on your licence but you would never get in trouble for that.
Like Aland said, Police only care that the insurance is held on the car for the person driving - if not then it is seized under S.165 Road Traf Act which means they can will take your car away (roughly £105) and then storage of £15 approx per day until you take out insurance for it. After 14 days, it will be crushed. You can also disclaim rights to the vehicle at the roadside to save the cost of seizing, etc (but only worth doing if you car is a banger).
If you come to make a claim and you are not residing where you have told them, you will prob end up with a bigger excess of around £500.
