[Ashlandchris]

Right. Time for an update.
I stripped all the front down and based on the advice here I managed to get approx 1.5mm of shims onto the servo saver so it tightened it slightly. I then refitted it all but the same issue seemed to exist. It would turn right, but not left. However, the servo saver was not causing this - it seemed that the throw of the servo was uneven. I checked the servo horn and it is vertical although doesn't look even in terms of action.
After checking that the transmitter wasn't set wrong for EPA on steering I swapped the Futaba servo for a savox which did exactly the same.
In the end I have had to alter the End points on the transmitter to increase left to 125% and reduce right to 89%. This gives me now exact equal steering so hopefully that is job done!