Hey! It's always a tough question to answer because the answer depends on the person, the course, the subjects (exceptional circumstances).
Uni's have to have a certain number of students on their courses, otherwise they get fined for having too many, or too less. If the course you're applying to has 140 places but 80 applicants, they're going to be a lot more lenient than if it was the other way round.
Unfortunately, how lenient they're gonna be is out of our control - I need AAB for my course but realistically think I'll get BBB. Just work as hard as you can now, enjoy summer, and cross that bridge (if at all) when it gets to results day.
(One thing I thought I might mention is that Russell Groups are usually less lenient than other universities - partially due to the increased number of applicants, however my friend got into Newcastle with BDD when her course required ABB - so it's certainly not impossible.)