Thanks everyone, I got the drum off. I looked again for the adjuster opening, nothing, felt were it should be was sunken in but something hard not rubber was blocking it. I then stuck the wheel back on and tried to use it's leverage to break the drum free, that worked for a half a turn. I then took a hammer and hammered up from the cooling fins of the drum to work it loose, took some time but off it came.
The self adjuster was caked in brake dust, grime and rust. Remembered why I hated drum brakes, and bought a the brackets to maxima conversion now.