@ TheMellowLife
Take this from a 26 year old guy who is only just starting out on his flying training (that's me, by the way!); do not worry about time. It is not essential to be in the right hand seat by 25 or you will have missed your chance.
Airlines today can pick and choose whoever they want, and by passing the aptitude tests and having good GCSE's, A-levels and a degree will simply put you in a bracked with a thousand other people. What will set you apart? Why should they pick you?
My advice would be to go to Uni (for me it was a great experience) but make sure you do a proper course i.e. not David Beckham studies or whatever it is nowadays.
In addition, join the University Air Squadron (UAS) as you can often get flying through that, similar to the Air Cadets. It will also set you apart from other people, and you may even like it so much that you join the regular RAF for a term and then come to airlines at a later date.
Either way, nobody knows what the airline industry will be like next year, let alone in three or five years, so just try to get yourself into a position to take advantage of any upturn in fortunes that may arise. And do your utmost to not rely on tens of thousands of punds of debt before you start!
Though that is just my opinion of course...!!