Hi Angus,
Your best bet would indeed be a clutch extractor. They are sold by nearly every parts dealer.
Just make sure to have the right TPI. Before using it, take out the bolt, and grind it down a bit to get a smooth surface so you won't damage the gearbox shaft.
When tightening the extractor bolt, just don't be to heavy handed. When it gets tough, don't force it. Give the bolt a tap with a hammer, and tighten the bolt again. If that doesn't work it loose, leave the tension on for an hour or so, and try again. Taper shafts can be very stubborn.
What was the state of the clutch plates? If they where very oily, this already may be the cause of them sticking.
The fact that the inner drum turns rough is a bit worrying, because this may point towards a gearbox problem. Could that have been the noise you heard?