its the flights that is the problem Dean. All the budgets airlines have gone a bit silly. Shouldn't be a problem to find availability over Christmas but its pretty full from 28th onwards.
I would say for a short break you'd be better off booking separates - most operators seem to offer week long trips.
Have a look for flights first - as SW points out they will be your biggest cost. If you can get the flights for a semi decent price, the good folk on this board can help you with the rest - transfers/accom/hire/passes etc... for any of the main BG resorts.