I don't know whether the interviewers will have seen your individual module marks. However, the absence of a merit/distinction, along with a 2.2 might make things more challenging for you. It depends on how much competition there is for the PhD.
As you can't do anything to change those grades, I would focus your energy on what you *can* do, namely to prepare well for the interview and ensure that your referees are supportive. In terms of interview prep, be able to talk confidently and clearly about research you have done. They need to be convinced of your ability to deliver a three year project (where success can be as much about project management as intelligence/grades) and your degree marks may be offset by a confidence and convincing performance at interview.
Good luck. :)