Hi i hold an offer from the University of Leeds.
To be honest, there is no definitive answer. It depends on a variety of factors: the grades of the rest of the cohort of applicants, so how many people meet the offer, how close you were to the entry requirement, if you have done an extended/ independent research project or an outstanding personal statement or have clearly shown incredible enthusiasm on applicant day. If you needed AAA and got AAB with B being close to an A, they'll likely take you anyway. Anything much below that and they'll most likely reject you.
But don't take that for granted, make sure you do your very best to meet the entry requirement.