Complex sentence: It has not formed an independent unit of civil administration, however as population grew a separate "St Antholin, Nunhead" ecclesiastical parish was created in 1878, with a church built in 1877.
Split into simpler sentences: It has not formed an independent unit of civil administration. Instead, as population grew, a separate "St Antholin, Nunhead" ecclesiastical parish was created in 1878, with a church built in 1877.