Travel Industry Services - Travel for Travel People It's not a massive discount but offers trade prices for industry related jobs. I took my family of 4 to Oz this past Xmas on BA. In total for 4 adults tickets £3000. Probably could of got it cheaper on another carrier but there were no hidden extras and it was peak time of year.
My advice would be when you've registered and you want to book a trip, phone them up because most of the time when you enter your trip details the search fails to find availability for your dates.
Good luck!