>>2 going to middle school, or being educated at a middle school level is a legal requirement in the UK. Beginning with the class of 2014, it is a legal requirement to stay in education until 18.
Now down to Infitx's problem. I just got my results today too, and I'm quite happy with them, so I won't lie and tell you I know how you feel. But I will tell you what I've been telling all my friends. GCSE's don't matter. Well, they're important, but as soon as you complete A-Levels or a college course, that qualification will make your GCSEs useless. Don't get me wrong, your hard work wasn't for nothing. GCSEs are only needed so that you can get more, even better qualifications. So don't stress over GCSEs.
As for what you should do, your local school/college can, and very happily and readily, will give you guidance and advice. I know it seems a bit late to be wondering what to do, but trust me, there are so many people in the same position. Just email, ring or visit your school/college and ask to talk to someone about your next step, they will be very understanding.
When you said about how your mum would kill you; just remember that they are your GCSEs, not hers. They are either your battle scars, your war medals, or both. If you feel you didn't do well, use your results as motivation to promise yourself to never get results like them again. If you did really well, make sure you maintain that level of focus throughout your entire educational journey. Don't stress over GCSEs, since you will be laughing about them in a year or two.
I hope that helped, also, I hope your results went well!