Awww don't worry. I remember when I did my UKCAT 2 years ago, I got an awful score, and I came out of the test centre crying my eyes out and I kept crying all the way home in the car as well! It does at the time feel like this is the end of your medicine application and that there's nothing else you can do, and I remember thinking I bet the other applicants at my school probably did better than me etc etc. It's NOT the end of the world whatsoever. please please also remember this, the UKCAT has no bearing on how smart you are or whether you will be a good doctor. A testament of this is people who retake their UKCAT a year later when they are on a gap year, very often people go from getting a low score first time round to something crazy like 750 second time round- it's still the same person sitting the exam, the only thing that has changed is they are more familiar with the exam, and the exam they sit second time round, the questions may be easier etc.
Remember you can sit the BMAT and apply to 2 BMAT universities (or more if you're brave enough!) Doing less well in the UKCAT does NOT mean you will do badly in the BMAT. I sat my BMAT and did a lot better than the UKCAT, you have a lot of time now till October so you can even start preparing now for the BMAT if you want, look up youtube videos offering advice (Sarah Yasmine is a good one!) and student room threads.
To this day, I will be forever thankful that I did badly in my UKCAT, the reason for this? If I had done well, I would have never done the BMAT and would have never gotten into Imperial College for Medicine. I am now so glad I did the BMAT as I am having the time of my life at Imperial. Trust me everything happens for a reason. Your priorities now are deciding whether you want to do the BMAT, writing an amazing personal statement and applying to a personal statement university as well and nailing your A levels.
Even if you do less well in your BMAT, put it behind you and focus on your A levels, its hard I know, but at the end of the day believe me it is the A levels that are the most important. Medical schools don't care if you've done the UKCAT or BMAT twice (They won't know!) because you took a gap year, but what they do not like is retaking your A levels. So whatever happens this year, focus on acing your A levels, if you ace your A levels you can take a gap year without having to worry about your A level results. I know everything seems a bit miserable right now and daunting, I felt the same way, but it will all be okay, just have patience, try your hardest and whatever happens, happens. Just please don't be too upset about your UKCAT, its done now, just look forwards from now. Easier said than done, I know! Message me if you need any advice etc