Thank you for the replies everybody! I have declared my diabetes to both the university and my tutor from the very beginning, although the latter seems to think it is all in my head. The test kit is currently not allowed because it is "an electronic device with the capacity for memory or storage", although that is an ongoing project - although I suppose even having it with me wouldn't have stopped the hypo! I have now emailed the most senior person in charge of exams, so if nothing else happens at least the issue has been flagged, again. I won't name and shame the university in question, but their attitude towards diabetes is a bit... well, it doesn't really exist, actually. Then again, we are talking about a BIOCHEMISTRY department where a lecturer stood in front of 200 people and said "the only way you can get diabetes is by being overweight". Sigh.
Honestly, I'm just annoyed because I'm in the process of applying for a Masters course that I'm really excited about doing, but failing this exam would throw that out of the window entirely!