Okay folks the case is solv-ed! Shortliner thanks very much for all your help. All trains running except one which is a missing a screw that holds the motor together so that's only to be expected. Another has mechanical problems with the driving wheels (Gra Far Class 37, the plastic cogs are sliding along the axels and going out of alignment, but that's what you get for buying Gra Far I suppose). The Minitrix A4 Pacific runs like a dream and probably always will, however one of the pistons has sheared off the wheel and I am unsure of the best way of fixing it. Great loco though. Well so much for flogging this on ebay... I AM GONNA BUILD ME A MODEL RAILWAY!
Thanks again everyone.
Neddle signing off.
PS Turned out it was the controller by the way.