OK. So I just gotvan email from Morgana that explains things a bit. It seems the tracking number format is internationally recognised, and googling it seems to default to USPS, who naturally don't have the number.
Try the Royal Mail tracking service, as the package was dispatched from the UK. My status there now reads '
Itemxxxxxxx
via International Tracked & Signed End-to-end tracking and signature on delivery
Status: It's on its way
Your item, posted on 11/12/14 with reference xxxxxxxxhas been passed to the overseas postal service for delivery in EIRE.
All good then!
Still not showing on the An Post Irish tracking service, so I guess it's still on the boat and hasn't reached their sorting office yet.
Long and short, try Royal Mail tracking now!