If they have offered you an equivalent loan vehicle for the period during which your car is being fixed then I fail to understand why you have refused this. Though the fault was present from day 1, they are telling you it is repairable so Clegg v Olle Andersson, House of Lords, 2003 probably does not apply. If you were to take the matter to court (at colossal expense) and if you were to get a ruling in your favour (not guaranteed) the dealer is still entitled to charge you for your use of the car for 8000 miles, though you could counter that with a charge of "wreckless endangerment" in allowing you to drive away in a car with a serious SRS fault. They might them counter that the light warned you of the fault and you should have brought the car back to them immediately. All a bit of a mess legally. Take professional (paid for) advice by all means, but mine is to accept the loan car and the repair and only reject your car if they fail to carry out the repair correctly. (If you were planning a foreign touring holiday then the dealer has to insure the loan car for you to undertake that.)