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?).
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).
The British Listed Buildings site has photos of the fort and boat approach with stairs, picking crane, and sloped ladder lift for getting loads from water to gate.