Hey Camdener!
I would have thought that being in London you were best placed of anyone in the country to find like minded/aged musicians!
Have you done much research starting with your school? Where do the musical ones go? What do they read/watch/listen to?
Once you can begin to answer these questions you will know how to target the people you're after.
Alternatively, go round to every music shop, coffee bar where musos hang out, etc and leave an advert "Looking to form a band! Influences are ............ I play guitar and sing looking for Bass, K'bds, Drums (etc). Contact:.............."
I know you are a multi-instrumentalist, but you need to decide what you want to do in the band and keep the rest to yourself FOR THE TIME BEING - so you don't put people off (if people think you are streaks ahead of them in ability they will be put off contacting you!).
Have you thought about starting an Open Mic session at a cafe or local youth club if you can't find an existing one? Either you keep it acoustic or have to sort out a PA, but a lot of venues will do that for you if they can hear the till!
Don't give up! Don't become disheartened! There is plenty of scope to get this accomplished, but it might not come together to your timescale; in the meantime, learn from the results of everything you do to bring this project home!
Oh, and Break a Leg in getting this sorted!
<-----<< On an even field, only talent prevails! >>----->
Gans Gwarak da yn dorn yu lel, gwyr lowen an golon!
>>-----> [color=#FF0000]Rudhes[/color] hag [color=yellow]Owres[/color], Kajima <-----<<