I need to rotate the content of the mapView according to the compass value:
float myHeadingValue = newHeading.trueHeading;
and for rotating
I've solved it creating in Interface Builder a smaller UIView and putting the MKMapView into it. The new UIView does not show the leftover map.
There may be an issue with the google logo being out of shot doing this though. Apple have contacted me to say that my app contravened the guidelines because the google logo was invisible.