A very interesting post Moss, and once again I am reminded that I must visit Anglesey soon.
M Scott Peck's account of his visit there back in the 1990s In Search of Stones was inspiring (though other parts of his book flawed) and I recently read Boudica by Vanessa Collingridge in which, using the evidence from such finds as the LCB Hoard, she was able to build up a picture of life in Iron Age Britain. She wrote a graphic account of the Roman invasion of Mona/Anglesey, drawing as all historians do on Tacitus, but balancing the 'propaganda' aspect of his account.

I thought perhaps the Hoard may have been related to the Roman invasion but having had a look at the Museum of Wales site (see below) I learnt that "such votive offerings are part of a long tradition in Bronze and Iron Age Wales"
Llyn Cerrig Bach Hoard at Museum of Wales

It seems that the island of Mona has a unique history which in some ways sets it apart from the mainland in general - so yes, I think the Llyn Cerrig Bach Hoard should go home.