As long as you get your referee to mention the car accident, you should be fine. GCSEs aren't the most important part of the application process anyway, and since you have a good reason for getting mostly Cs, they shouldn't hold it against you. The only problems, as others have mentioned, are a) your D in GCSE maths and b) the fact that neither university offers politics, so unless you're interested in either PPE, SPS or politics and history and can prove you have the ability in maths/history, you can't apply anyway. I'd recommend researching the courses in detail and then resitting GCSE maths as well as maybe dropping a subject and picking up AS history if you go for the politics and history route.