Ahaha, I thought so too when I first got here. The content and learning style here is way different from what I was used to back home! A 40% is the passing grade here (I think around 65% is the equivalent in the US?), the bare minimum, and you're kicked out of uni or made to switch to a different course if you don't at least pass your first year. I was so used to getting 80's and 90's back home, when I took my first test here and got a 60 I nearly screamed; but all is well! A UK 60% = B range, which is 80% for the US.
80's and 90's are super hard to come by here (even the lecturers struggle to achieve a 90-100 after taking the same exact exams as us!), so I've really had to work on readjusting myself to the new grading scale.
As for volunteers though, I can't speak for all courses that have experiments, but in our third (and final) year of Biomedical Science we have to conduct our own research experiments and we get to ask all uni students if they wanna volunteer for it. We have these things called
practical classes (or practicals for short) - each course has them - and the medicine & science courses all have practicals in the form of lab work. In these kind of experiments, we all have to do them for a grade so no volunteer stuff their (unless we're working in small groups, where we get one of us to volunteer
become the victim and we zap them with electrodes or something).