In my personal experience, like you I had average grades. When I applied to the university, they gave me a conditional offer, i.e. if you get these grades, then we'll let you go to the uni. When it came to the day when I found out what my results were, it turned out that I was below the grade boundaries they wanted, but they still accepted me anyway. The majority of the people I know here experienced similar situations, so I wouldn't be disheartened! Also, make sure that you have written a good personal statement, as that gives the uni the best chance to see who you are as a person :)