My mistake. GAPAN is £15 cheaper than OAAs. Its a one day 2 hr test. OAAs is 2 days with SIM, COMPASS and TECH tests, team exercises and a 2 on one interview.
You also get debriefed one on one with the GAPAN tests and they have no interest in it other than to make you realise if you have the aptitude or not. OAA on the otherhand will be making a very healthy profit out of you should you meet a
minimum requirement.