Daniel,
Going home at the weekends is absolutely feasible and, if you're trying to hold down a relationship or marriage, probably essential. You could go home every night and stay with your folks if you wanted to, but you would miss out on the socialising and study benefits that you get by staying in halls.
As for A-Level grades I was fortunate enough to get 4 A-Levels at grade A (blush
). A-levels are probably the last thing that BA will look at - everyone who gets past the application form screening already has the minimum qualifications they need. BA will be more interested in you as a person and your flying ability.
Hope this helps
eeper