Sorry to here of your woes, I suffered the same misfortune when I was building my NCF Diamond. My remedy was to start the car in first, pick up a bit of speed and then jump on the clutch and brake at the same time, there was quite a bit of rubber on the drive before I succeeded. Also had it with an HA van but the above solution did not work so it was gearbox out, clutch cover off and the clutch plate had to be prised off with a screwdriver.In both cases the engines had been stored outside under tarps. Good luck and I accept no liability!