[OJFord]

Shipped in surely, everything else would need to be anyway. The flushing toilets etc. mentioned as a challenge probably use a rainwater collection system or perhaps seawater (I'm not sure if the latter's done, desalination probably necessary?).

[bombcar]

You can run toilets on seawater just fine, maybe some slightly different seals.

[OJFord]

It was corrosion to pipes I was thinking of. Though perhaps if nothing existed already they'd have been allowed to use plastic pipework (highly doubt they'd get listed building consent for replacing existing with plastic).