How it got sorted
Engine was running fine - then did its old trick of misfiring like a ...... and then cut out altogether.
Having changed dizzy cap, rotor arm, leads, plugs, ignition module I poked my hand under the dash and eventually found by gently pulling on the loom to the ecu I could make the problem come and go - dashboard out - sorted out the wiring and it hasn't misfired since! Also my ecu was mounted on the ford holder thingy and was vibrating like a vibratey thing - put in a piece of dense foam between it and the chassis tube to dampen the vibration which I think caused the problem in the 1st place.
Just when I was ready to throw my toys out of the pram as well