There are BMAT unis and UCAT unis. If applying for Oxbridge they only take the Autumn BMAT so after you apply so in effect you apply without knowing your score.
Then they all have different weighting and how they select using different criteria so you need to work out best fit for you.
Exeter until this year used to interviews everyone with 3 x A* predictions. This year they didn't and their cut off UCAT was 3050 rather than 2850 in other years.
Some use gcses to get you through first stage and then don't count them again. Some still retain them in later rankings so if your UCAT is less secure you may choose them.
The good thing is they are very transparent about how they rank. The difference this year was 21% more applicants and a higher number of second time round with high grades in hand, which saw a higher UCAT than usual needed at some.
Last year one uni even changed their criteria after 15 October. I can't remember for sure possibly Leicester or UEA? This obviously was not usual or helpful!
So you definitely need to open up Excel and map it out.