If you show that you have the aptitude, leadership qualities and intelligence required you will be encouraged to apply for a commission. Even if you are not encouraged keep trying. If you do not have the educational requirements then the service will help you to acquire them. Take part in team sports, being a member of the ships football, rugby, boxing team helps develop team spirit and character.
Best of luck in your pursuit.
A fair proportion of RN officers originally joined up as ratings.
Selection/promotion of suitable ratings is an important means of maintaining the right number of officers.
Opportunities to become an officer continue until you become quite senior, can't remember when the cutoff occurs and you become too old (someone'll know).
Forty six it is for 'Senior Upper Yardman" silverfox. One former WO of my acquaintance says he had more influence in high places when he was a WO than he has now as a 'grey' Lieutenant. There is something to be said for making the move early.
Thriller, there is a pretty big window of opportunity for a capable, driven 'youngster' to become an Officer. Nothing is handed to you on a plate though and you'll need much more than a well kept kit, like Slim said.
Seriously, by all means make your ambitions known early on but I'd suggest you make a big impression first (but never at the expense of your class/shipmates) then if you haven't been pinged as Officer material, then let your DO know that you are keen.
Be well read, well informed and articulate. Aim to finish at the top of your class in everything (not necessarily smalll arms and PT) but help out the less able, always. In civvies, dress like a grown up without turning into a young fogey. No tweed.
If you wish to be a officer why don't you just go direct, as once you're in uniform as a rating you will be constantly scrutinized if you try to go the CW route. The direct route/ application will only look at you as a civilian if selected for interview at the AIB, whereas once you're signed-up you will be looked at from numeerous angles for at least 18 months -2 yrs for suitability when the pressure will be on you to prove yourself. Good luck!