Complex sentence: The group was named after Primrose Hill in North London as the core members of the group lived close to each other as young actors in that area though in reality the social focus for the group was the Notting Hill area.
Split into simpler sentences: The group was named after Primrose Hill in North London. The core members of the group had lived close to each other as young actors in that area; the social focus for the group was really the Notting Hill area.