Hi John,
I just tried the dizzy with a bosch hec715 bluebird replacement coil.. the difference in the curve through the rev range was a beautiful thing.. alas it is still sputtering through certain rev ranges under load.. the only thing i could think of trying next would be replacing the module..
opened the casing and the wires to it all seem fine and newish!

seeing as ive had some amazing people help me out with parts and take time out to give wonderful advice I'll be going back to points and am happy to be doing so! but just thought i'd let you know i'd eliminated another factor and still no luck..

the prob is most certainly electrical.. wiring the ballast resistor will be interesting (thanks for the instructions) because i have a positive from the coil to the dizzy and negative from the coil to the dizzy and then a cream wire also connected to the positive which i can't trace back (it heads off into the loom but im assuming it's 12v+)

but as such! will have a brand new (used once around the block to test, bought this morning and have the reciept hec715 to sell very shortly either separately or with the dizzy!)