You can buy an X1 package from either your travel agent or from costa direct. your travel agent has to contact costa to buy it, and you pay for it when you buy it. on your costa card it has X1 typed on it. you can buy 2 drinks per card so in theory one card will do a couple!! we paid £83 for one card in feb 08 for 10nights. it includes unlimited bottled beer, wine, bottled water and cans of fizzy juice only when in an area serving food. however there is usually a grill area opened till about 4.30pm most days. we found it great value, hope this helps you.
The X1 is such great value PLEASE do not be tight and buy one per adult.
Just bought an x1 drinks package for 2 people on the Costa Concordia sailing 9/9/08 it cost me £105.65 for 2 people for 1 week(including service charge). I am told that you have to purchase in advance no later than 5 days before, but I do not know if that is correct. I booked and paid for it through my travel agent .