AW - the RN has been known to be more sensible about hayfever/asthma than the light blue, who are so concerned about their two-winged master race status that even a pimple on the ar$e might be a blemish too much.
As it happens the aptitude score required by the Navy is actually higher than the RAF, it seems. While the pass is 112 for pilot, the actual minimum for getting a place at Dartmouth for RN aircrew is about 130.
The extra-curricular activity should have a team/group, not individual focus, ideally have a leadership component, and should be physically and/or mentally challenging, and be a considerable personal commitment in terms of time. Exposure to people from all walks/backgrounds is particularly good.