Thank you for your reply.
If I meet my predicted grades, I will be able to achieve both of them. I won't disclose my full entry requirements, given that this is in public and just in case people can work out who I am. What I will say is that although the wording of the offers may differ slightly, their difficulty is about the same. This is where the problem of choosing between the two lies. Durham has a subject specific requirement, but lower grades. With Nottingham, I can fulfill the requirements in any of my subjects, but with higher grades. They are also going to give me an unconditional offer if I Firm it.
I am not sure how much you know about the U.K. Engineering league tables, but Durham is number 5 and Nottingham is number 6. On a whole though, for all subjects, Durham is higher up.
Plus, I am still waiting on a decision from one more university. I am trying to think ahead, in the eventuality that I do not get an offer from there.