it's definitely worth it. all the best places require you to do a foundation (though they will say that they still consider A level applicants you would be put right to the bottom of the pile), and either way it's such a fantastic year. i'm just finishing up my foundation now, and i knew 100% that i wanted to do illustration for my BA when going on the course, but it's about the experience and things you learn, not so much about choosing your specialism! you work in completely new ways and i've learnt so so much since finishing my A levels, not to mention it's allowed me to get some amazing offers. so yes, i 100% recommend. also, if you were to not apply to a foundation course and find yourself without the offers you wanted for BA, you would have to pay tuition fees if you did it a year later as the course is only free to under 19s, so don't make that mistake!