Furdez,
I doubt you'll find anyone who'll go into much detail on it, partly because there's not a massive amount to tell but partly because you can figure the rest out for yourself so us telling you it all is unneccessary
.
Format-wise (if it is still the same as a year ago) then you fly out 1 day, get taken out to dinner as a group that evening and then each have an individual interview the next day, a tour of the office, before flying home.
In my experience it was not very different to other airline stage 3s, it's NJE's chance to look at you for themselves and the interview is not unpleasant. And I say this as someone who failed the interview too
Best of luck if you're called forward!
BM