Yes. I had also received an R&R after my viva and eventually took 2x6 month extensions. I asked my doctor to personally write to the university (he had to do it twice) in order for me to get these extensions on medical grounds. The university staff even called him to confirm that the information on the letters was true! I suppose they do that sort of thing, because otherwise people would get extensions by using fake letters.
I also gave the university a letter from the hospital, as I was hospitalised for a few days. Also, the paper that the ambulance gave to me, when they came to collect me after my health suddenly deteriorated. There was plenty of evidence there to convince them that my health problem was a genuine emergency and destructed my studies.