Wannabe,
A lot of people I know had not flown anything when they joined up so it is not a bar to progression.
If you really want to become an aviator go for it. Start the ball rolling now-failure at aptitude or AIB stage means a wait of a year before applying again. If the worst should happen use the downtime to address the reasons for failure, and also do your travelling then. The AIB especially will want to know on your second board how you have spent your time since the first one. And if you are successful first time round then yopu will be quickly on to one of the most enjoyable and rewarding careers you will ever enjoy.
One other thing you need to think about before applying:
The RN is an armed force with a lot of people currently deployed in hot sandy unsociable places. Your job may well involve the use of lethal force-how does that sit with you? Think about how you would react to the use of force, as it will certainly come up in the AIB.
Good luck for the future.
CTF