I third it. I know it's painful waiting for your results, but everyone of us who is at Oxford went through the same situation and we didn't get people to vote whether we'd get in or not of we missed our grades.
Instead if worrying about it (there's nothing you can do after all), just make sure you have the numbers for your admission tutor (both Oxford and your insurance) in your phone (and maybe clearing number too) and make sure you're prepared incase the worse happens. Otherwise, just go and enjoy your holidays as you'll end up working bloody hard when you get here!