In the USA they have Lemon laws introduced for this situation, with 4 new rads and no fix you would be able to take your car back and get a refund even if the car was outside it's warranty as you would claim the car is not repairable. Unfortunately in the UK you would need to rely on the Consumer protection act which is not car specific and does not go far enough, however a case could made that the manufacturer new of the faults at the time of production and would then be wide open to a civil action.
