My Next step in fashion design?

Don't know about the best college but you certainly need to go, their really is two ways you could go. Straight into fashion design or into textiles. I would find your nearest college that provides both courses and give them a call to arrange to go talk to the tutors, take some of your drawings with you and get their advice on what course you should take, from their it's all research on your part. Don't take a forum's advice on which is the best college to go to, you need to go visit them and talk to the people on the course to get the bigger picture.