you CAN tow on the motorway but there are rules.
Max speed is 50 mph for towing another motor vehicle
You can only use lanes 1 & 2 so no outside lane.
The basic controls of the vehicle must be working,
so brakes, lights, indicators, steering, etc
when you say there is no interior, the car needs to be in a safe condition for a driver, so proper seats and seatbelts, no exposed sharp edges inside or outside. the bumpers need to be on and the car must have a windscreen.
As a recomendation I would tow on a rigid bar rather than a rope, if you have to buy a bar then hire a transporter/trailer it will be about the same money.
tax and Mot are not neccesarry if you are taking it to have its MOT or to Have work done to pass an MOT, As for insurance i would check with company that covers the towing vehicle to see what they say, most will cover a caravan/trailer etc but may need notification if its a car.