A great place to spend Christmas - we do it every year.
I agree with the posts regarding checking accommodation availability, but also check reviews. Pictures can tell lies, and Barbados accommodation can range from awful, disgusting places to paradise on earth.
My preference if not booking as part of a package would be to rent an apartment/villa - you get much more room. For example, for a 10 day stay, two of us can rent a very high standard 3 bed apartment for the cost of a 4-5* resort.
Flights are horribly expensive, usually £1200 rtn economy LGW-BGI, so the Dublin ideas look great,
For December this year, we have booked Club on outbound and First on inbound with Avios. Due to there being little or no Avois availability, we used double points as GCH and used up 500,000 Avois (plus £969 taxes, fees etc)