Soak shaft in Penetrene or WD40, leave overnight, then you actually stand inside the bowl, and twist back and forth as if dancing, which will then free the shaft. This is the only way of freeing the shaft.
Replace the hose to the top of the bowl at the back while you have this all apart, and have access. The hoses deteriorate and now is a good time to replace.
cheers
Jenny., December 2008