I want to do a computer science degree but...

Hey guys, I need advice. I'm currently on holiday in Canada and not a second goes by when I'm not panicking. Basically I want to go into computer science but I'm worried I haven't achieved high enough. I took as levels, where I did badly and got BED in sociology, geography and APPLIED ICT. Now I took applied ICT thinking it was going to be more hands on ICT which is what I like, but it's more like business studies so I never really enjoyed it and never got stuck in. Now I'm approaching the end of my a2 year and I've applied for a foundation degree in computer science at my local course offering a 120 UCAS point entry requirement. I can easily get this I am confident, however I went to the interview and they were very impressed. They then asked for a D or higher in applied ICT for my final a level. I talked to my ICT teacher and he said I should get this but I am absolutely swamped in work at the moment and all I can think of is not getting the D and what the hell am I gonna do after?! So I have a few options. I was looking at trainee jobs, now the first question is do you need a degree for a trainee job? Secondly I was thinking about retaking year 13, but then I thought they are only interested in my ICT so could I use my year 13 year to retake year 12 and year 13 applied ICT at the same time? I'm sure my school would let me I just need some advice because I'm getting really down about this and I'm not too sure what to do anymore, thankyou guys.