No official statement on beach metal detecting was found. The council pages found cover only seasonal dog exclusion zones at Roker and Seaburn (1 May to 30 Sept, PSPO) and a review of the Port of Sunderland byelaws.
We couldn't find a published rule. Foreshore owned by the Crown Estate follows the Crown Estate's terms; for council-owned beaches, ask the council before you dig.
Tap any spot in England on the UK Detector map to check it against scheduled monuments, SSSIs, nature reserves, National Trust land and access land in one go. Free: 3 checks a day.