According to an article in BP, his tours are at noon and 2:45: take a look at this.

Just show up. I think there is a morning tour (11ish) and an afternoon tour approx. 2:45...if memory serves me correctly. There is a sign (English tours) located in the entry of the church to the left just outside of the souvenir shop. Mr. Miller will just show up at the designated time. The cost is approx 10 euros (cash only)per person that is collected before the tour begins by Mr. Miller himself. Enjoy!

No web site or e-mail, but here's his telephone number:

011-33 2 37 28 15 58

As Al said, however, you really don't need an advance reservation--just turn up for one of the two daily tours.

Cecile.....I doubt if you'll find anything. MM is a "one man show" that most probably doesn't have a connection to a computor. But I dont think an advance purchase will benefit you. Just get you to the church on time!

Thanks for help re one day barge trip. We decided on the St. Martin from the D'Orsay. Now...
Do you know if a reservation can be made before we leave the U.S. for a tour of the Chartre Cathedral with Malcolm Miller. I can't find anything on line (except raves). Thanks Cecile