The Religious Life of London, edited by Richard Mudie-Smith and published in 1904 lists the Woodgrange Road congregation under the name "Zion's Watch Tower."
As reported by those attending, the congregation consisted of sixty-eight men, sixty-two women and fourteen children. Given this proportion of children to adults, one might suppose that the congregation tended to be made up of older individuals. I'm not certain that any other conclusion can be drawn from these spare statistics.
The "public hall" located there was King's Hall Cinema. It had a seating capacity of 250.