Batter the fuck out of it at both ends mate, its the initial shock that will help, then with you turning it with your breaker bar get a friend to go hammer crazy on it,

Heat it up as much as you can, but unless you have gas welding gear i doubt you will get it hot enough,

Got mine off with an impact wrench like i said, the bolt freed its self up with the shock loading the gun put on it.

Failing all of that, don't cut it, take it to some one with a hydraulic press and press the first half of the bolt through.

Best of luck mate!

Rob,