Looks like I've found out what the problem was.
I've replaced the ignition switch for a 'car' type switch that you twist
the key right round to start. All the electrics turn on including power
to the ignition unit on the first click, however, when you turn the key to
start it, it cuts the power to the lights etc to give you max power from
the battery, & yes you've guessed it, I took the power for the
Ignition off the same feed so cutting the power each time the starter
was engaged!! Doh!
Have now remedied the feed & am getting nice blue sparks from the plugs