Its probably worth calling some universities that you are interested in - or just any that have Interior design...are you thinking of taking a degree?
I would have thought that a course would be interested in seeing a portfolio of work and ideas etc before you are accepted - most creative courses are more interested in your imagination, ideas and design rather than your grades - however these do still count. I am in the last few months of a Graphic design degree - most people on my course would have had to take a foundation course (1 year) in order to get a portfolio together to get onto a degree course.
Hope this helps, Goodluck