as an mot tester i can tell you that as long as the axle is mounted to the car and the bushes are not hanging out then it should pass fine, there is no reason for rejection for axle not mounted straight or any way for an mot tester to check as some one said some cars are like that from the factory others because they have had panels replaced badly. you might find that if you have had a funny rattling noise from the rear that has now gone, one of the spring end may have broken off and now fell out. hope this helps cheers mike