flaz if its moving side to side its gonna come out eventually, i think you are gonna need some help from a mucker tho to stand at the front of the bike straddling the front wheel to stop it moving side to side, then just keep on working on it steering the bars side to side and at the same time pulling up......it will prob be a slow and labourious task but as i say, if its moving slightly it not frozen in there so to speak. try using dieslel too, its what the vee-dub guys use to free 30 yr old ball joints on beetles....good luck fella, if you dont have any luck with that method, try the old wheel off and a drift up the bottom of the forks onto the bottom of the quill method.....large hammer needed....
any way enough of this useless drivvle im of to remove my stem easily.
Dave