"No" - Simon's answer every time Mark asks a question that starts with "Do you remember...?" or "Have you seen...?"
Possibly, this is because Mark's cultural references are unashamedly highbrow. Indeed, one suspects that some of the arthouse films that Mark namechecks are so obscure that only Kermode and the director have ever seen them.
Alternatively, perhaps Simon does understand the references but is feigning ignorance in order to better represent the average listener, and to maintain his choric role.
On occasion it also seems possible that Simon is saying it to wind up Mark, as Mark will become increasingly exasperated at Simon's refusal to accept he must have seen a film, or must be aware of the thing to which Mark is referring.