You may have trouble finding Banns Books, even if you know which of the many churches it was.
The Parochial Registers and Records Measure 1929 only required that register books of baptisms, marriages and burials in the power and custody of any minister of the diocese shall be kept in a chest or safe,
Banns Books are not mentioned .It is only since 1978 with the passing of the Parochial Registers and Records Measure, Registers of baptisms, marriages and burials and
registers of banns,confirmations and services are, when completed have to be permanently deposited at the Diocesan Record Office. (usually the local Record Office). Where Parish Archives remain with an incumbent they should be available for inspection 'at all reasonable hours' and fees are payable, by law, as set out in the 'Table of Parochial Fees'
Durham Record Office have very few Banns Records see
http://www.durhamrecordoffice.org.uk/Pages/InformationLeafletsItem.aspx?LeafletRef=17 More recent parish books may still be kept in the parish church.
Stan