Apply or defer due to chronic illness & surgery?

Hi, I was wondering if anyone had any advice for when applying to uni with a chronic illness/disability?
For year 13 so far I've really been struggling with my health and this is then having effects on my revision for mocks in January.
So far I have offers from 4/5 unis and my firm will be Nottingham - they've offered me AAB but also will take A*AC or A*BB, so I'm not too concerned about getting the grades and I can always throw external circumstances at it.
I'm currently undiagnosed by having lots of tests & appointments these days which will hopefully give me an answer but are contributing significantly to the fatigue - alongside this, my symptoms are joint pain, significant digestive issues & full-body cramping. I suspect ulcerative colitis despite some anomalies with the symptoms.
The issue is, I also have an upcoming surgery which has quite a long recovery time. My two options are either have it in June or appeal to the surgeon to have it moved to just after my mocks due to the distress the additional condition is causing me. If the tests reveal an additional condition, this may even affect what surgery I need to get.
If I have the surgery early, this will take me out of school in the months before exams, but this will mostly be revision and I can work at home (had to do this for my GCSEs) - however, if the surgery goes wrong I certainly will not be able to sit my exams, which was my surgeon's reasoning for postposing the operation.
However, if I have it the week after my A-levels, not only do I have to live with this condition and the emotional effect until then, I risk it worsening. Plus, I'm concerned I wouldn't recover fully in time or be totally free of complications by the time I went off to uni in September. (Plus I'd miss the A-level summer, lol).
Should I just take a year out and get the surgery either time?? That has its own issues - I really was so excited to go to uni and had previously been campaigning to go despite my health. Plus, I have a twin sister and most of our friends are going to uni, I'm not sure about the emotional impact it would have on me all seeing them having fun while I'm at home for a year - a year is a big commitment. But what if I can't manage my continuing symptoms if I go off to uni this year?
Blahhhhhhh so much to think about, if anyone else had experienced uni with a chronic illness, taking a year out or having surgery in the middle of revision season/term, please help me out!!! xx

I haven’t experienced exactly what you have experienced but I had a similar sort of circumstance during my GCSEs where I had a surgery in December which lead me to being off for a couple of months (and I was still recovering for about 6 months) so I was severely behind in revision. It was during COVID-19 so we all did mock exams which sort of formed our predicted grades, as well as the teachers considering coursework etc. So it was a little different, but we made sure the school took into account that I had been ill and recovery had seriously affected my ability to revise. Considering your circumstances you would probably be able to resit/ sit your exams later on once you’re well enough. When I was wondering whether to postpone the surgery, something that helped me was just thinking your health comes first. When you’re in it school and college and uni feel like the biggest things in the world, but really it is such a small part in the grand scheme of things. If you do decide to take a year out (which I also did but for an unrelated reason), a year is a very short amount of time and it will fly by. Prioritise your health, that is the most important thing.