Regular readers know my affection for the series of prayerbooks first arranged by Charles H. Leonard, Universalist minister and seminary professor, and later extracts and abridgments. The first dates to 1867; the last, a local extract, was printed in 1957. I type out the collects and readings from the former each week.
Careful readers will also my suggestion that, for very small and minister-less Unitarian and Universalist churches, especially the older ones, I recommend reviewing the old church school literature for worship forms and themes. The structure are simple but churchly, the themes timeless (good for congregations that meet less than weekly) and are easily "matured" to an adult or mixed-age congregation. The Beacon Song and Tune Book serves as an analog to the hymns and services of the "old red" Hymns of the Spirit.
Now I have just found a parallel to "Dr. Leonard's prayer book": Sunday School Hymnal with Offices of Devotion (1912). It's not quite as evergreen as the Beacon Song and Tune Book but this nearly hundred-year-old book wasn't meant to be. I'd use it as a resource book: to see what psalms and gospel passages work together to make a service. The prayers, at first glance, can beÂ abandoned and replaced, once the themes are recorded.