Brut force and heat ruled the day :-) All barrel bolts were removed using an old imperial socket an impact driver and a blow torch. As for the rotor, I took it to my local garage, who put a air powered socket on the bolt and had the right extractor to pull the rotor off. Had to force the fiver into his hand too, well worth it.
So I'm now the proud owner of a box full of bits (neatly labelled) and another box of casings ready to get washed. On a quick glance, nothing looks too bad. Yes, I've got a buggered cam and need new cam chain slipper blades, but everything else looks OK (no missing teeth, cracked casings, loose bearings sort of thing) Obviously everything will get a thorough going over before getting re-fitted, but I think this motor is worth persuin, which means one happy Squirrel :-)
Will keep you all posted and thanks for the tips guys.