Did you sit new style GCSEs or old style ones? Your post is a bit unclear. It's very likely next year unis will have to look at GCSEs differently as less people will have the very top grades.
Durham don't have any official GCSE requirements beyond a pass in English language, but obviously they will compare your academic profile with other applicants.
It may also be, depending on your actual grades, that predictions of A*A*A* would look unrealistic to universities, and wouldn't help you that much. A strong score in the LNAT would definitely help.
Ultimately, I'm sure you would have a chance and having one or two risky choices on your application is ok.
You have a chance. Your GCSEs won't be a huge problem, your predictions would be good and if your LNAT MCQ and essay is good, then definitely.