This is my blog about unfounded requests: https://2040training.co.uk/a-cure-for-blindness/
This is a link to the ICO’s *draft* code of practice for Subject Access: https://ico.org.uk/media/about-the-ico/consultations/2616442/right-of-access-draft-consultation-20191204.pdf
The best place to find UK course decisions is run by BAILII (the British and Irish Legal Information Institute), and it is a superb database of court decisions, and I have listed the most interesting ones below. All of them are worth reading if you have the time (Durant with a big pinch of salt), but I think Gurieva and GMC are essential reading for people who deal with Subject Access.
Gurieva 2016: https://www.bailii.org/ew/cases/EWHC/QB/2016/643.html
Ittihadieh 2017: https://www.bailii.org/ew/cases/EWCA/Civ/2017/121.html
Dr B vs GMC 2018: https://www.bailii.org/ew/cases/EWCA/Civ/2018/1497.html