foundation year at UAL or regular course at birkbeck?

i recently finished sixth form with not so good grades (CDD). i wanted a computer science related course that was in london and through clearing the best ones i got was a regular 3 year computing undergraduate course at birkbeck or a foundation year in CS at UAL. i really don't know which to choose, i heard bad things about birkbeck like i won't like it because i am a young student and its full of older people so i wont get the proper university experience, aswell as it not being that great for CS and because im young the evening study wont be good for me but to me birkbeck doesnt look that bad and I know UAL is probably a better place I feel like a foundation year is me essentially wasting a year of my life, but on the other hand maybe a foundation year would help me get used to university and help my studying get better so i do well in university? im really not sure and im really looking for some advice please help me