Generally the larger organisations won't be too interested, H&S requirements, 145 competency assessments and so on, best to look at GA or small business jet MROs, they may be interested n a free pair of hands to help out.
You might write to the small companies at Lulgate or Staverton, as mentioned, log everything in your work experience log book, however minor.
Out of interest, what is your availability, do you study full time and just want weekend work, or can you spend 2 weeks at a time working in the hangar?