Thanks for the quick reply wiggy!
Well thats what i wondered as if APU could provide redundancy to the hydraulics.
However , as in "flying the big jets" and from "http://ads-b.ca/777/B777-Electrical.pdf"
they both didnt mention APU as a backup source for the hydraulics while did mention that for the RAT...
Therefore its hoped some experts here can shed some light on the issue.