Ok so this is weird. I just refitted the old pulley but without a washer in behind the big plate that sits under bolt, it binds up and won't spin. Had to fit the washer in behind the plate to allow it to spin. I'm starting to think a previous owner has fitted the wrong part. Not sure if I now try and EP001 as the tensioner might have enough to take up the extra 8mm needed to fit a smaller pulley.