Complex sentence: A new church nearer Brynsiencyn, St Nidan's Church, Llanidan, was built to replace the old one between 1839 and 1843, as the old church required significant repair, and the growing population in Brynsiencyn needed a church closer to their village.
Split into simpler sentences: A new church nearer Brynsiencyn, St Nidan's Church, Llanidan, was built to replace the old one between 1839 and 1843. This was for two reasons: the old church required significant repair, and the growing population in Brynsiencyn needed a church closer to their village.