It is important to remember that redundancy is about the post, not the person. Is it that this work has ceased or are you looking to dismiss him on the basis of his conduct or capability in that the work is there but he isn’t performing as required?
You cannot select him for redundancy based on him being part time or his performance. If you are considering making the post redundant then you need to consult with him about the reasons why and the alternatives to dismissing him which includes pooling him with any full time employees who do the same job before selecting for redundancy.
Why after two years is his performance suddenly not acceptable? Is this a role that is supposed to generate income or is it one that stops you losing it? Be sure that you are reviewing this correctly and that this is a redundancy issue before you go down this route.