A level resit

I am going to resit my A levels as I did worse than expected. In December of yr13, my aunt was diagnosed with bowel cancer and had to undergo a major operation. A month later, my grandmother passed away, which greatly affected my studies and concentration in the following months and was partly why I didn't do so well. If my teacher mentions this in my reference will universities still consider me even tho im a resit applicant?
For context, some universities I am hoping to apply to are Warwick, UCL and Bristol for Economics

I’m in a similar situation. What grades did you get and what subject are you hoping to do at university?

Bristol - Extenuating circumstances | Study at Bristol | University of Bristol
and other Unis will have similar webpages / forms.

Do I upload the form along with my UCAS application when I apply? Or can i do it now?

For all Unis, you send their form directly to them, not UCAS - but at the same time as you send your application to UCAS.