Kings...
I would hope such a building was wired 'sympathetically'.
Hide all wiring where atall possible.
Where its not possible to hide the wiring then MICC would be the best way to 'blend-in' electrical requirements in a building which wasn't ment to incorperate wiring when it was originally erected. However, I bet there has been a fair amount of 'destruction' to parts of the building already due to past gas and electrical additions. Try to cause the least amount of damage to the building as you can (use previous cable runs / drilled holes where suitable).
Im very surprised you will not be dealing with 'English Heritage' and be getting some proper guidance in regard to whats required. This is our nations history your dealing with after all. I would make a few enquiries before you start this job. A phone call to 'English Heritage' wouldn't go a miss. This is the only number I have for them, but someone there will point you in the right direction of who to speak to.....02392 856 728.
I would love to be part of such a job.
Good luck with it and I hope it turns out to be a great installation.
All the best.
Edit.....
After a little more thinking ive come to the conclusion that if the wiring can not be seen then conduit is fine, but it mustn't be seen too much, in my opinion. (High-up in the roof etc would be okay I spose).
also......mechanically unprotected pvc/pvc, in positions which couldn't be seen, will probably end-up causing future problems due to vermin.
Rather than shiney metal-clad sockets / accessories (or god forbid white plastic ones), have a look at whats avaliable on the market, something more subtle, less obtrusive, less shiney.
Sympathetic to the building is the key here I think.