Does your Priceline confirmation indicate what type of rooms you were assigned? One King, or double? You shouldn't have to pay extra for a 3rd person unless you request a room change (from King to double) then they may have the right to charge an additional fee since they only guarantee double occupancy. That shouldn't mean you can't have three stay in a room IF you were assigned a double room. I'm basing this on my past experience with Priceline (in the USA). I have the same issue - looking for rooms in January pre-cruise for a family of 7. Most likely need to book 3 rooms with Priceline, then I still may have one King room sleeping 3!
