All the way through elementary school, high school, and undergraduate college, i used to study like crazy for an exam. When i took it, i found that most of the stuff i had studied was NOT on the exam - so basically i had wasted my study time. In addition, there were about 12 kids in my class, that never seemed to study, but got straight A's, or nearly straight A's. I couldn't figure this out!! When i ended up in graduate school years later - the same effect occurred. I figured out that, if i didn't 'clean up my act' - i wasn't going to make it out with a degree! Thinking about it after a couple of drinks - i realised that what i had to do, was to figure out what the instructor thought was important - because that was what he was going to put on the exam.
Each time he discussed a particular topic, i kept track of how long he addressed that topic, and how much work he did whilst he was addressed it. As an example: Just talking about something is easy. I assigned a 'work factor' - as a metric of how much work he had done - of 1 to 3 for just talking about something. Drawing on the board is harder. I assigned a 4 to a 6 for board drawing. Say he talked about a topic for 5 minutes - a 'medium' complexity talk (something that he had spent some time organising, but not a lot). I would take the 5 minutes, and multiply it by 2 - for a medium complexity talk. This gives a total of 10. Then, later, he spent 9 minutes drawing a diagram on the board relating to the same topic. I would give him a 5 - for a 'medium complexity' drawing. Multiplying by the 9 minutes gives 45. Adding the 45 to the initial 10, gives 55. I would continue this for every time he mentioned that topic during the grading period. I would do this for every topic he went over in class during the grading period. Then, i would 'rank' all the topics, from the highest total to the lowest. Then, i figured how many questions could be asked on the exam. Figuring an hour for the exam, and that it typically would take 8 to 12 minutes to do each problem - there could be 4 to 8 questions on the exam. I would take the 10 highest ranking topics, and make sure i could answer any question that could be asked on each of them - questions that had shown up on homework problems, during class discussions, or anything else.
The first time i did this, i had 100% of the exam questions on my 'sample' exam. It took me 12 minutes to do the 1 hr exam. I checked my work 3 times. The first time i checked my exam - i found 2 small errors. Correcting them, i checked it 3 more times. Finding no other errors, i turned it in. 100%.
My 2 'study buddies' were amazed. I had showed them my 'sample exam' about a week before the actual one, and they didn't like any of my questions: "Oh, he wouldn't ask that - he asked it on the mid-term".... (me): "Yeah, but nobody could DO it on the mid-term & he ended up yelling at us. Don't you remember that???" After the exam, they asked me: "How did you DO that"?? Easy!!
Try that - it may work in the Uk too. Best of luck!!