higvin8, You are 100% correct in suggesting Blyth for 'Bishops Quay.' Google - 'Bishops Quay Blyth' and the first reference to come up is the Port of Blyth website> History, and it confirms that Blyth Quay was originally know as Bishops Quay. There is also an old map shown re the layout, long before the harbour was built and extended over the years.
Also check 'Blyth History' here in Roots. There may be reference to the quay together with old maps and drawings of the harbour, etc.