I agree with James, you don't stand a chance of getting onto a marketing graduate scheme unless you have some hefty marketing experience through either internships or working in entry level marketing department jobs. They are simply ultra competitive.
I also recommend applying to small businesses to help run their marketing / social media. You should also decide the areas of marketing that are most interesting to you and improve the relevant skills, e.g. if you want to work in online stuff, improve your IT skills and stats / maths. Learn about Google Analytics, start a blog, etc.
There are so many good marketing / PR jobs out there in medium sized businesses.