large molegrips attached to the exposed bit and pulling and twisting motion, if that fails hold the grips at 90 degrees and give them a whack with a hammer to shock it out.
If the doors have just been recently stripped they will have sat in a caustic soda bath for a week. If so let the wood dry and shrink back and they should open up.
Try putting something like an old Allen key though the lock hole and using that to help push/hammer it out.
Are new locks going on? If so marry up new locks to those so you have a template of maximum area covered by new lock and chisel out a bigger hole to get better leverage.
