Quickly from Wikipedia:
Christadelphians hold a view of Biblical Unitarianism. (source)
But that leaves us with the question was is "Biblical Unitarianism"?
Today, biblical Unitarianism (or "Biblical Unitarianism" or "biblical unitarianism") identifies the Christian belief that the Bible teaches God is a singular person—the Father—and that Jesus is a distinct being, his son. A few denominations use this term to describe themselves, clarifying the distinction between them and those churches which, from the late 19th century, evolved into modern British Unitarianism and, primarily in the United States, Unitarian Universalism.
The history of Unitarianism was as a "scripturally oriented movement" which denied the Trinity and held various understandings of Jesus. Over time, however—specifically, in the mid-19th century—Unitarianism moved away from a belief in the necessity of the Bible as the source of religious truth. The nomenclature "biblical" in "biblical Unitarianism" is to identify the group/s as not having made such a move. (source, emphasis mine)
Although, I do not know anyone from this group, the definition of the group and their belief on the Trinity would seem to suggest that they do not hold the doctrine of the trinity.