Jambone,
BA will be taking some guys/girls who have just done 'A' levels. They will not expect an 18 year old to have been head of the Olympic Delivery Authority and to be able to to discuss the change issues related to a newly elected mayor. They will expect an 18 year old to tell them about how they dealt with disagreements within their scout patrol; or how they overcame adversity on a DoE challange; or dealt with some sort of cultural issue in class/scouts/some club you were in.
Probably only 1 in 100 applicants will get a place. It will be tough and BA will only take those that it considers the best. However it will be fair in-so-much-as BA will expect those applicants in their mid 30's to have done much more in life than those who are 18.
Use these 2 years to get out and do stuff. Get up to your local flying club, volunteer for things in your local community, get a Saturday job. These things will show BA that you have what they want.
All the best