Never seen the point in extenuating circumstances really, I'll be applying this year, even though it doesn't seem to make much difference. I believe that all they do is round your grade up if you fall short a a small % at the end of the entire degree, or if you fail, they'll maybe be more lenient when it comes to letting you do a resist/let you back in etc. I understand that if you fail an exam and have extenuating circumstances, they'll still cap your exam at 40% anyway. You should apply for a delayed first sit which might be a bitter option. Check with your uni though, everywhere is likely different. At my uni it basically means nothing.