Need to retake yr 13 modules. Extenuating circumstances

Hi, I'm current in yr 13 and I am doing my exams at the moment. I know I'm not going to get nowhere near my potential and my grades are going to be pretty bad sad to say.....reason being I have got an extenuating circumstance. I want to apply to the university of manchester but haven't applied last year but will this year, with bad grade, I will have to retake quiet a few modules. I have also completed this programme by manchester university called MAP I have got addition 40 ucas point and I have also got a reference assisting my application to the uni by a post grad student and it is good as I got full marks for the programme. So will I be given a conditional offer for manchester? If I put down the extenuating circumstance and the fact I'm retaking modules. Really want to get into manchester! I want to apply to optometry.