JamieMac,
Of course, it shows you have a genuine interest in basic mechanics. You need to remember, you're still young! You have so much time to become an airline pilot; especially now when the economy and recruitment is at an all time low.
If you join the RAF you'll learn much more about aircraft than any University or College could teach you, you'll gain experience and skills you wouldn't get from anywhere else, it's a secure job, get a nice pension from it, travel the world... what else could you ask for at 18/19/20?
When you do go for your first job in an airline how impressive will it look for the airline that they have a young lad whos served X amount of years with a fantastic organisation, getting the best training in the world and working with some of the best pilots in the world.
My mate was laughing about it, a couple of years ago he was fixing Fiat Puntos now he's fixing Fastjet aircraft worth million of pounds.