[RCHunt]

I had the bright idea of swapping the components within the float chambers around but again after running for a few minutes it started chucking fuel out of the forward carb overflow. I think that shows that the fault is not with the components.
Like the idea of excess fuel pressure, no time at present but will check this out next week.
It just seems odd that everything worked fine before removing and refitting the carbs without doing anything to them.