Josephine! - Restoring a Joe Waugh ladies tourer

My new plan is cut it like a karate chop across the diameter until it looks a load of chop sticks poking out of a bike (you can see where I kind of started in the last pic).. then bend the chopsticks in a bit with locking pliers.. and finally try and get a sharpened screwdriver in there between the post and the frame to chisel them out.
Any other ideas before I start?

Bad idea. I've done similar before and what will happen is that the 'chopsticks' will just snap off and you'll be in the situation you're in now, but with the post flush with the seat tube, making your life all the more miserable.