OK, I got the aeroplane to its natural position (disassembled on the bench for repairs / modification) and had another look at the tail wheel assembly. I think that I can blame the recent steering issue on myself, not providing enough "flat" for the steering horn screw to sit against and therefore the the wheel was steering uncontrollably. This is now fixed, and I have also replaced the pathetic foam tail-wheel with DU-BRU 1-1/4” Tail-wheel (Cat. No 125TW) and had to drill the centre to larger diameter to fit. Finally the whole Tail-wheel assembly give me some confidence. I will have to wait and see how the aeroplane taxi to be fully convinced it is all resolved.
One other modification at the tail wheel area to allow easy access to the wheel collar screw (the wheel collar that holds the tail-wheel from falling off by gravity) was to drill a hole on the side of the aeroplane where a black dot was on the covering. This probably saved 1/2 hour of frustration trying to access this screw.
I have also removed the fuel tank to see how far the oil spill from the carburettor breather travels inside (attached picture). Not good... I have coverd with epoxy the whole fuel tank bay so it will not soak into the wood too quickly and hopefully will drain from the holes I have at the bottom.