Thankyou everyone for your advice, I really appreciate it.
I logged on again to " Manage a booking " & hey presto our FF no has been added, looks like one of the agents I spoke to at Etihad
had enough wit about them to add the no. I also called the travel agent ( it's an actual shopfront not online ) & they assured me that it should be fine.
So thankyou everyone for your thoughts & advice, & wish us luck, we've never flown with Etihad before ( we usually prefer Qatar or Emirates ) so not exactly sure what to expect on a 14hr flight.