Hello Frank,
Brian compiled his wills index to assist people using local Family History Centres, run by the Mormons (but open to all). They bring the films in for you to view and/or copy for a small fee. The number on the end of the index ref is the film number, which differs from the numbering in the Manx Museum.
You can find your local FHC by looking in the local phone book for "Church of Jesus Christ of Latter-Day Saints".
But before ordering, check Ian Radcliffe's website as well as Brian's list to see whether anyone has already transcribed them. And when you have seen the films send the transcript to Ian to add to Brian's list for the next person!
lawsonsiom.freevar.com/
Sue