Kieran, I can't tell from here whether the axle shaft is mild steel or a heat-treated higher strength alloy. You can tell by applyiing a file to the exposed end of the shaft (don't remove a whole lot of metal, of course). If it is a heat treated alloy that has yielded, its strength will never be the same again unless it is heat treated again after straightening. However you do not seem to have a lot to lose by making the file test, and then making a decision.
