OK got to grips with cleaning the spray bars. First filled them with break cleaner a few times. Then stuck a pin through the holes to clear them out a little. But found the best way was to go old school and mouth to mouth on the exit holes and blow through them until they're perfectly clear. Now I have mocked up a little petrol bath and leaving them in there to soak over-night to melt any other crap that might be in there.
This is the first time I have clean spray bars. I would definitely recommend it. Dead easy to do. Mine were not completely blocked, but were a little gummy and will definitely lubricate better now. They are like new now. This was a fairly clean engine, so a dirty engine will probably have been blocked worse than mine. Free mod that keeps engine alive at the end of the day so a no brainer.
After that carried on painting a few more parts.