There are probably about 20 threads about this film on Cathinfo.

The film is easy to find on Youtube, but the only DVDs you're likely to find of it are of the bargain bin / dollar store variety, without subtitles or separate language audio tracks.

Also here: http://www.gloria.tv/?media=4874  
1Hr, 13min  English
Posted by Iacobus  15/04/2008 03:22:33
..In the near future, the Catholic Church has joined with other western religions in an ecuмenical movement that has washed out much of the original message of the true religion. A group of Irish monks have begun saying the mass again in Latin and have begun to have an international following. - Martin Sheen is sent from Rome to bring them to task.

The story line is very faithful to the 1972 book "Catholics" by Brian Moore.

Catholics (The Conflict)
UK 1973

Director:
Jack Gold

Cast:
Trevor Howard (Abbot),
Raf Vallone (Father General),
Martin Sheen (Father Kinsella),
Cyril Cusack (Father Manus),
Michael Gambon (Brother Kevin),
Andrew Keir (Father Matthew),
Godfrey Quigley (Father Walter),
Leon Vitali (Brother Donald)


Amazon seems to have it on DVD as "Catholics" and "The Conflict" here
http://www.amazon.com/gp/product/B0007XSXFY/ref=as_li_tl?ie=UTF8&camp=1789&creative=390957&creativeASIN=B0007XSXFY&linkCode=as2&tag=httpwwwchanco-20
and here
http://www.amazon.com/gp/product/B000R9AKR2/ref=as_li_tl?ie=UTF8&camp=1789&creative=390957&creativeASIN=B000R9AKR2&linkCode=as2&tag=httpwwwchanco-20
but these versions seem to suffer from cut scenes (such as the opening gathering for Mass on the coastal hill, or the last several minutes, etc) according to reviews at Amazon.  I was going to buy one until I saw that production/editing information.  I'm not sure a full version is available anymore.