Demand for new homes is entirely from mass net immigration, there is no excess of births over deaths in North Somerset (ONS data).
Immigrants move into central Bristol and the White British population move out to areas like North Somerset which is 97% White British (2011 census):
Percent non-white British in Bristol
NSC seem stubbornly unwilling to acknowledge the cause of demand.
The ONS attribute 73% of UK population growth directly to net immigration and 27% to more births than deaths. Immigrants have the highest birth rates.
The government's target of building 200,000 homes per year to meet this demand means building over 152 farms per year. Don't be surprised if the next one is near you.