Just spent about 2 hours of mixed daylight and darkness trying to see why Edward II is running like a bag of s**te, and failed.
current theory is that the distributor is shagged, causing the timing and/or the points gap to arse around enough to put the fire out. I don't think it's fuel, as 1) the carb was pretty clean, and in any case I cleaned it just in case; 2) the symptoms are intermittent (but enough to make it a pain) and 3) when the fire starts again it makes impressive bangs and sheets of flame from the exhaust, which leads me to think that it's the sparks that are missing.
Changing coil and condenser for other ones makes no difference to the fault symptoms. There is quite a lot of play and movement in the distributor, it has to be said, compared to what there should be.
Anyone got a decent series III distributor to sell?