I am going to side with the condenser crowd. We had the exact same symptoms on my Dad's Tudor. Bout drove us nuts. Then it would be fine. Then it would do it again. Finaly he blew his exhaust sytem up and called me for help. After cleaning the carb six times, going through the fuel system and all the usual suspects, I grabbed my spare distributor and headed out to where he was stranded. Popped it in and she ran like a top. Once home he swapped a new condenser in his original sparker and after six weeks of fooling around with everything,( ignition,points, coil, gas cap, etc) all was good. I had asked him to try another condenser and he said he had.........another old repop one with what must have been the same issues. Since then we are both packing brand new and tested units for an emergency. It can't hurt to try right?
Hope it helps, Cheers!