I did the same, my choices were Oxford, UCL, KCL, Bristol and Cardiff. Put Oxford (AAA) as my firm choice and Bristol as my insurance because they made me an offer of A*AA or A*A*B. If you’re confident you can achieve your predicteds and they’re in line with mock grades then it’s unlikely you’ll get less than AAA so I’d go with the unis you really want instead of applying to a lower grade one just in case. Unless you really want the peace of mind of knowing you have a certain uni place for if everything goes badly wrong.