"The debt rests with the administators of XL. The aircraft are leased and owned by another company that will not be responsible for XL debts. It is all a little unneccessary but gives a little power to a BAA goon."
WRONG! All debts remain with the Aircraft that have incurred them!
Its the same a driving your car through a speed camera, the car registration is sent the fine!
If the owners (lessors) want their Aircraft released from each Airport then its them that have to stump up the cash for any debts.