Progress update, had PCM and Dash back to BBA to test/confirm all ok, which they did FOC for us. On refitting, the engine was still not firing or turning over on key. Started looking closer at wiring loom, found when touching or moving engine loom (especially where it goes round the back of the block), the dash would go crazy with instruments and faults everywhere also when PCM Plugs 'wriggled' this caused much the same symptoms. I unbound part of the loom (hoping to find one broken wire to repair) but naturally no luck - I did get the impression that someone had undone that part of the loom sometime before in the cars history. The result of gently moving the loom a couple of times was to loose all connection to PCM (including with my diagnostic unit). Decided after talking to a couple of local auto electricians, that a loom repair was not practical - so ordered a new engine loom from Ford which took them a while to get (when ordered they said it was in group stock so would be the next day). Fitted the new loom last weekend, which restored all the PCM/PATS/Diagnostic connections and stopped all the fault codes coming up when the loom moved. Frustratingly, having got that part 'stable' again, the engine will still not turn over on the key (or fire when starter operated direct). I'm thinking now to take a longer harder look at the wiring back from the front fusebox. hopefully the gradually lighter evenings will speed this process on!