Wow,
So it appears that i'm not the only one having problems trying to work out how to remove the platen knobs. There are holes in the knob, but they are not screws and as they do not continue right the way through the knob i can't see that they are split pins that can be pulled out!!
There is probably a stupidly simple answer, but i can't see it right now.
Again, any help, ideas would be appreciated,
Alan.

I have never attempted to dismantle one of these, but I do know what you are talking about.  I think that it might have been assembled in the factory and then a pin driven into the hole.  I can't see what else it could be.  If this is the case, I would drill the pin out very carefully (and pray that it isn't hardened steel)  Before reassembly, clean up the hole and tap it with an appropriate tiny thread.  Although not original, it would make sense to tap out with a metric thread - there would be a better range of screws etc. available in metric.  Then screw a tiny allen screw in to replace the pin.  Please bear in mind that this is speculation, not based on having done the job myself !