If you don't have any other work experience to show, then I think you should put it on your CV. Don't list them all individually though. Indicate that you have participated in sessions of varying length and depth between certain dates, or starting from whenever.
Think about what you have gained from these experiences which can be used in another job - in other words, what are the transferable skills you have gained.
Depending on what type of jobs you are applying for, and assuming you did gain these from your experiences at UCL, you could mention such things as reliability, objectivity, ability to follow complex instructions, team-working and so on. Whatever you put on your CV, make sure that you can demonstrate and provide examples of in an interview situation.
When I applied for my first full-time job after University, I detailed various Saturday and holiday jobs I had had while a student. My first boss said that this impressed him favourably, as it demonstrated that I was able to commit to something and follow it through. Although the jobs themselves weren't relevant to my new career path, the fact that I had them was a positive factor which worked in my favour.