Just to feedback on the thread and say thanks to all who've helped along the way, as always.
Having done one side, I flew through the other.
I've bled the system a good few times, front and back. One of my rear cylinder bleed screws was stripped so I've welded a nut onto it. Not the prettiest, but it's doing the job.
I've got quite a long pedal at the moment, but the brakes are effective. I think the fronts will get stronger as the pads bed in.
I think the long pedal is an adjustment problem with the rear brakes. I've adjusted them so that the shoes don't catch the drums but they must need to be a little tighter.
My drums spin freely, I've read some posts that say they should only spin once and then stop - I would be interested to hear how others adjust them.