IT'S ALIVE. turns out i was the carby. 28/36 weber going on hopefully on the weekend. Thankyou everyone very much for your help.

it is working. i had that disconnected once before and the car wouldn't idle. the car is going to a mechanic tomorrow, so hopefully he will fix it asap

Sure is, to test it put the ignition on and unplug then plug it back together, should make a click sound if working ok.

is that the little soleniod on the front corner of the carby nearest to the rocker cover, if so yes it is hooked up.

Have you got the anti-diesel solenoid hooked up?

Tan is good, ideal mixture.
I still think it is electrickery

when it plays up it has no power and sometimes stalls if at idle. pulled the plugs out just after it played up and they were light brown, indicating a lean mixture?? they are normally a bit black when i check them.

Since you say that you have had the carb. rebuilt, I'm guessing that it is not a fuel problem.
It sounds like you may have an electrical fault in the ignition primary circuit.
[sounds like your secondary/high tension side has been rebuilt]
Have a good look at the wires going to/from your ballast resistor and even the resistor itself.
Wriggle everthing while the engine is idling and see if there is a miss/cutout.
Can you describe what happens when it goes wrong, engine dead, still running, no guts or what?
Aways difficult to diagnose from a distance, but ....

i just worked out, when it does play up the fuel level in the bowl of the carb does not drop. does that mean it is not a fuel supply problem?

sounds like a possability. was your problem intermittent aswell?