I suspect if the engine is not common in Australia you may have problems finding an engine tuner. I don't know if Caterhams are popular down under, as Peter said, the latest ones use the Sigma in various states of tune and you may find some ideas there.
A shame that Ford should be so off about helping you. I suspect they'd be the same over here as well. But, it is their engine and if your car is still under warranty I believe it is them that warranty the engine, not Morgan.
Good Luck!
