A word of support. I screwed up my A levels by basically never turning up (I discovered music, drinking, smoking, cars and no good women

). Got B,D,E. Ended up going to Bournemouth Uni (originally was going to Southampton), had the time of my life, got a First, then walked into a job with IBM (arguably one of the best companies a software engineer can join after uni).
It's important to do your best, but if you don't get the grades, IT REALLY DOESN'T MATTER. There are lots of alternative courses and paths, and only the most hardcore of positions (e.g. lead scientist at hardcore mega cutting edge robotics company) care about which uni you went to. The remaining mortal jobs care about you having a good degree result and they care about your character and personality. Where you got the degree from is far less important.
Good luck with your results!