FYI, Jersey is not part of the UK and has its own laws and legal system. So, the British law regarding discovery of treasure like this would not apply. Jersey is a separate state governed by the British monarch. The Channel Islands are what remains of the Duchy of Normandy still ruled by British monarchs. Its laws are a mix of French and English law.
The Islands are much closer to France than England and were the only "British" territory occupied by Germany in WWII.