Update.

I have managed to get hold of some carb cleaner & cleaned the ISCV out.
I have also replaced the rubber gasket that sits behind it as the one that was there looked pretty crusty.

It hasn't performed the flicking between 800 - 1250RPM trick yet, but it still feels like it could be idling a bit smoother.

I have a set of Magnecor 8mm HT leads on order, as I'm going to see if it makes a difference, paid £45 for them.
Mr Ford wanted £17.50 per HT Lead!! (well 3x £17.50 + 1 x £18.50) = £71 for the set