After trying to go out in the pi last night and other instances of misfire and uneven running that have shown up dribbling/dripping injectors as a cause, I decided that new seals would be a good starting point. I obtained some new seals from Jason Chinn and after reading online how Jason recommended changing them, I decided to practice on a couple of spare injectors that I have. Above is a photo of the component parts of a Lucas injector. The small ring is in fact a circlip, which once removed allows the centre of the injector to be pushed back through the outer body towards the threaded end.
injector body with some WD40 (carb cleaner may have been best) and after lightly oiling I re inserted the centre back into the body.