From what I've seen first hand a concussion like this needs time to heal. Your brain, the organ responsible for processing information, has been harmed and needs to heal.
The main thing you need is time, which you seem to be lacking severely. That is the part I would focus on first. I'm not familiar enough with the UK's educational system to tell you how, but if you know where you want to end up try to find a way that gives you more time (whether that means starting later or starting something else and then transferring).