Thanks everyone, I didn't expect so many replies. The guys that fitted the Macerator Toilet, said to avoid them, but I assumed that's just because they want you to ask for a proper toilet and they can charge a fortune.
No, it's because they don't want to come back and fix the thing under guarantee, when the waste pipe is full of week-old fermenting ****. Or even worse, week-old fermenting **** under pressure.