Flo, may I ask who told you that you're not allowed to take Christmas Crackers with you?
I am there for Christmas and I fully intend to take crackers with me (considering you can take butane gas and petrol lighters I was amazed that anyone would have a problem with Crackers!) - I just checked the BA website after seeing your post and found this:-
<i>Am I allowed to take Christmas crackers and/or party poppers on British Airways flights?
Answer
<b>Christmas Crackers</b>
Each passenger is allowed a maximum of two standard-size boxes of Christmas crackers. British Airways Dangerous Goods department prefers that the crackers are packed in your checked hold baggage, but will allow them in your hand baggage if necessary. The crackers must be made by a reputable company and be in the manufacturers original packaging. The crackers must be for personal use only and not for commercial use. No homemade crackers or kits are allowed on board the aircraft.
Note: Any Christmas crackers taken on board aircraft must not be used during the flight.
All items carried on board an aircraft must be made available for all security checks.
<b>Party poppers</b>
Party Poppers are not allowed in hand baggage or checked hold baggage on any British Airways aircraft.</i>
Maybe it's just an airline thing?