Brilliant, thanks again, thats the sort of info I was lacking.
And agreed, leave well alone unless in trouble!, this was one seized (motor and gearbox). It is a bit of an adventure taking it apart, and you can tell which part spent more time submerged! Head etc all came apart like it was bolted together yesterday, gearbox is a different story ...
MSR should be ok, sounds like a jet on afterburner at full whack, glows to almost white hot so should do the trick. If it doesnt a few extra pumps on the feul tank should help

If not I have a propane torch in the shed somewhere, but am hoping the heat from the msr will be more uniform and diffuse, it has worked previously where propane has failed me!
Impellor was basically rotten, one side had a fracture allready and the rest crumbled with fingers. It was very corroded, and perhaps an indication that the driveshaft would be stuck solid in hindsight.
So on to the job of drilling out the pin I can not reach, I wish bendy drill bits were freely avaiable, although I may go through the housing and fill with quick steel later.
Oh and as for item 22, that one came out weeks ago! Just unscrewed with no problems at all, so at least that is out of the way. It seemed too easy so I guess brute force and heat will be next on the list.
Really am gratefull for the advice.
Mark
ps: agree on the drilll, handhelds into a aluminium housing are asking for trouble ...