Product/Industrial Design Undergrad interviews?

Are the deciding factors on whether you get an interview solely your AS grades and reference? Or is there some sort of way of sending your portfolio.

I don't think my grades at AS level are going to be amazing if I'm honest, and I'm worried that the admission officers will just scan though my application and see nothing of worth, then throw it in the bin and send a rejection letter.

The thing is, I've been told by numerous people that your Portfolio is more important than your grades, it's what shows you have potential; furthermore by the time I'm applying to university I think my portfolio will be really good - but if all they have to go by is your grades am I stuffed anyway?

Bit of a guess, but I could end up with:
Product Design: B
Maths: D
Physics: C
Chemistry E

I don't think I'll do any worse, but hopefully it'll be better...
So please enlighten me on whether its still possible to get a placement with dodgey grades!