This discussion fron 2007 might help, particularly the bit which says:
"All items taken from the coastline had to be reported to the Receiver of Wreck before 20 February.

Failure to do so could result in a fine of up to £2,500 and having to pay the owner twice the value of the item.

The Receiver of Wreck, Sophia Exelby, said about 1,400 items had been reported, which she said was a "fair response".

"I am reasonably pleased the majority of people have reported items and have shown themselves to be law abiding," she said."