Whether you’d have to take a two-year gap year is dependent on the universities that you plan to apply to and have already applied to. For example, Birmingham has said that for offer holders who do not receive the needed grades this August, when reapplying they would not need to redo the UCAT and interview and simply do autumn or summer 2021 exams (not both, but the grades do not have to be achieved in a single sitting meaning you can use a combination of your calculated and predicted). If you think August-start of October will be enough time to revise for UCAT, then technically you could sit the UCAT this cycle for 2021 Entry and only have to do one gap year than two with your exams then being in summer 2021.This is a confusing situation but check which schools are being as flexible and understanding as Birmingham. I would expect that not every medical School would require one to do a 2 yr gap year.