Sounds most likely that your dish has just 'twisted' either on the motor tube itself, or the whole lot has twisted on the pole. See if you can see which it is by any marks left by the twisting motion.
OK, this is not the prescribed method, but it may sort you out.
For a start, leave the up/down (elevation) position, and work on the side to side (Azimuth).
Power everything up, and select 1W on the receiver. Make sure the dish drives OK. It should end up in alignment with the 1W marking on the motor body.
If required, the dish should be slackened and then twisted on the motor body until it's in the 'middle'. There should be a vertical mark on the motor tube, or some other way of aligning.
Lock that off, and then slacken the motor mount on the verticle pole slightly. Twist side to side until you get the best signal on 1W (tune the receiver into BBC world, or other FTA). That should be pretty much due south. Lock it off.
Quick and dirty, but if it's just 'twisted' then this may fix it. The dish could have moved in elevation, but that's more unlikely.
That'll be £99.99 please! ;)