Scotty
Don't worry about your background mate. If you're right for the job it won't make the blindest bit of difference.
I know people in this job from wealthy families and I know guys from poor (and broken)families, and they all do the job equally well.
BV
PS. Don't be down hearted if you don't get it. You're still pretty young with plenty of time to get in.
I didn't get a 6th form scholarship. I then didn't apply till my fourth year of uni and got in straight away, despite many nay-sayers along the way trying to tell me that you have to be a demi-god to get selected. Just stay keen and don't let people get you down. Despite what all the whingers on this forum say it's still a bloody great job and I wouldn't change it for anything.