Well, I got annoyed and whipped off the dizzy cap and plastered it with some WD40 and also sprayed some over the coil lead and coil.
Tried it again (with fear that I had drained the battery) and after a few turns she coughed a little and then fired!
SO, I got up to Halfrauds and got some stuff and chucked it on (new HT leads / coil lead, dizzy cap and rotor arm) and doused those with WD40 as I fitted them on.
Now I shall wait and see what happens, looks like rain again tonight / tomorrow so that will test it.
If it still happens I shall try the flap thingy next.
Fingers crossed!