Hi Pilot CR,
I think it's great that you are so enthusiastic but I would say that there is no rush. First of all I would recommend certainly finishing your A levels first and putting all of your efforts into those to make sure you get the grades for FPP should you wish to go for it.
As for whether to go in for a pure "white tail" integrated course or an airline sponsored scheme, I would have said that it would be better to wait for a good airline sponsored scheme to come along and try for that first. You've got time on your side, if needs be go and get a job while you wait, build up some life experience. If the airline sponsored schemes don't work? Well then you can try looking at integrated later on.... but really I don't advise rushing straight onto an integrated course with no firm job promise at the end. From the timescales I seem to understand you'll only be 19 or so by then which is nothing really... it was 8 years between me leaving college and starting on an airline sponsored course so I wouldn't sweat about a year or so getting some work experience, to the contrary I would personally recommend it.
Having been through one of the larger training orgranisations and seen the stress that some of my friends have been through trying to get placed at the end, try and go airline tagged all the way if you can.
Cheers!