Complex sentence: Eileen Caddy, who had met Peter Caddy in 1952 at RAF Habbaniyah, joined them in London in 1953, soon Dorothy Maclean was to join in, thus at one point all the future founders of the Findhorn Foundation were part of her London group.
Split into simpler sentences: Eileen Caddy, who had met Peter Caddy in 1952 at RAF Habbaniyah, joined them in London in 1953. Soon after, Dorothy Maclean was to join in, thus at one point all the future founders of the Findhorn Foundation were part of Sheena's London group.