Thanks for the compliment Geo. I get call a whole load of different things during the average working day but rarely is "eloquent" one of them :D
Fair comment Charlie, there is always going to be that one screw that is a "special" case, either due as you say to corrosion, or because someone who shouldn't have been fiddling has installed it with Loctite and tightened it with an impact wrench set to max. :pulling-hair-out: Often as not in those circumstances I will declare it FUBAR and a more aggressive approach to removal is adopted on the grounds that the offending screw will be replaced, in which case anything goes so long as the the only thing that suffers is the screw.