I have put the 12v toilet back in and fitted a better design non-return valve.
The 230v toilet was OK but had its issues, principally the amount of water used. Since fitting this valve no backflow has been noticed. The other issue I had with the 12v toilet was voltage drop on activation. I have overcome this with a small sealed 12v battery in a cupboard very close to the toilet.
This was the original toilet swap blog.
It's a common joke in the UK that mounting a TV on the wall is a bit "Council House". It just happens on the boat I decided it would be a good idea as it frees the surface of the unit.
Much neater as all the wires are in the wall now. The extra height is better, more comfortable viewing angle. It was a bit low before.