It's September: The beginning of the oyster season :)
I Googled "oysters in Dorset" and found "a pearl":
"The crab house café", a shack opposite the sea with their own oyster farm.
Eat at "the beach shack" or buy oysters takeaway.
Oysters to start followed by grilled sardines infused with rosemary and a bottle of chilled Muscadet.
Finished by a nice walk following the mysterious sign "pirate lane..."