If the screw is pointing in to the middle off the tyre away from the sidewall id guess it was ok , Also the front rear thing id have thought as you steer with the fronts and in the wet etc I would go with put your best on the front.
Looks like from reading all the posts above I am wrong on both points. To be fair for £250 id just buy a pair and be done with it sell the old pair on sh*t bay wording it one needs a repair /puncture fixed and recover some cash there better to be safe and all that