Looking back, I've found it said once in the youtube video I posted earlier of Jan Marquis, and it is also included in the very first Learn a Bit of Guernsey French BBC recording.
From my amateur ears, they seem to be saying:
Jer - nay - zee - ay
Jer - is like the beginning of the name Jeremy
Nay - like the horse says "neigh"
Zee - the beginning of zebra
Ay - rhymes with "neigh"
Hehe, I will attempt IPA at a future date (once I figure out how to download the IPA font onto Linux).
Here's my attempt at IPA! (Font and consult courtesy of Suzanne - Thanks!)