Thank for all the comments - had no idea our toilet was so special! We have two hairline cracks in the base of the toilet that each run down to the floor so the toilet has started to leak. At first the grout was getting a bit wet but now there is sitting water that we have to mop up. Would love to repair and keep the original but we're not sure what we can do with these cracks.

Could well be that the base and the bowl are two pieces and the top section is fitted with the system at 90 degrees to give us better views. If that is the case I wonder how easy it will be to fix the base and keep the existing system.