All you need to do is get a proper geometry alignment done, not the crappy alignment done at a tyre fitter, Im talking the bells and whistles alignment where you get a before and after print out of all the various suspension angles.
The usual reason a steering wheel does not point straight ahead when driving straight ahead on a flat road is the THRUST ANGLE. Having a thrust angle out of line with the car centre line causes you to steer of centre to correct it.
A good geometry alignment can correct this easily.