The I'm A Celebrity... star went to stay at the farmhouse after he split up with girlfriend Sarah Matravers over his antics in the jungle with Matthews.
The former Catatonia singer and Bannerman were drinking at the Ship Inn pub in Trefin when Marc grew upset because a photographer was taking photos of him with Cerys.
He then allegedly took the camera from the paparazzo and removed the memory card from it.
A witness said: "One of the snappers got a photo of Cerys and Marc in the pub and then he got back into his car. But then Marc and a male friend of theirs came out of the pub, opened the door to the photographer's car.
"Marc eventually got hold of one of his cameras and took it back into the pub with him. He then took the memory card out of the camera. Then the friend came back outside and gave the camera back without the memory card in it.
"Marc and Cerys obviously didn't want the photos of them getting out."
Spokespeople for both Marc and Cerys have not yet commented on the reports but Dyfed Powys Police confirmed that they were investigating an incident.
Bannerman is also facing accusations that he hired prostitutes and took cocaine while he was dating Matravers.