A quick thanks to Keith from Aquafax www.aquafax.co.uk
I was passed their details by Mastervolt, the company who makes my isolation transformer. Remember that saga? Its the earth and neutral point all over again. It turns out that I was right. Their documentation (page upon page of how to bolt it to the wall and very little on the wiring) is basically misleading at best and wrong at worst.
The output of the Mastervolt isolation transformer does require the earth and neutral to be connected together on the output and both then connected to the hull. I know it says it in the documentation but the diagrams say something different.
Big thanks to Keith for spending the time to help and you have certainly gained a new customer.