Use a piece of clear plastic tube from the bleed nipple into a clean container. Part fill the container so the end of the tube is submerged. Smear red rubber grease or Vaseline around the bleed nipple to stop air being drawn in through the threads and crack it open about half a turn. Pump the pedal a few times keeping an eye on the reservoir level. Repeat until the plastic tube is full of fluid with no air bubbles then close the nipple, you should then have a working clutch. The pedal won't go firm as I've found the Commer clutch to be quite light, but you should end up with about a half inch of travel at the slave cylinder push rod. You can actually do it on your back by pulling the pedal from underneath and keep an eye on the bleed tube at the same time.
I've used the same method on my vans and my Mini with equal success no need for up/down open/close, I even bled the brakes on my Morris traveller the same way so I know it works.
Good luck