Read the link, dont run the car with mixed tyres on the same axle and run flats require a pressure reading system or must not be fitted to the car.
One run flat and one ordinary on the same axle, could affect the insurance as well.
Did they balance the tyres when they fitted them, just seems strange you had to check the pressures.
Just Googled run flat and found this, have a read, I,d think I might go back to the fitter and go for the specified ZS180 tyre. :-
http://www.blackcircles.com/tyres/runflattyres
