Thanks for the replies everyone, has been a big help. The engineer I checked with said it will be OK with 2 wipers. Cobra's in NZ are being passed with just the 2.
"Technically" though I have the feeling they do require the 3 - as Rebel said depends on the engineer doing the inspection.
I found this link in my hunts, looks like pretty good coverage to me with just the 2......
Wiper Coverage
More info from the same site....
Cheers,
Dan