I made a christmas cake November 2006 and still have it
It was stored in greaseproof paper /foil and plastic container /not refrigerated
Am I right in thinking if I re-iced it it can be eaten?
In days gone by the first tier of a wedding cake was saved and used for the first born christening cake

Refrigerated? I know people who freeze the top of wedding cakes for 1 year anniversary...

It depends on what the Christmas cake is made of? Traditional English Christmas cakes, like fruit cakes with some kind of alcohol in them last a long time if stored correctly.