Lauren25:
We have had couples that had broken up whilst planning our wedding for long times and were assured they was not getting back together so "free the space up for the wedding day". I did this-on 4 occasions! Now slowly but surely they are asking for the wedding list to be tweaked again so their partners they are now back with can come again!
Honestly, I'd tell them that you've been more than accommodating (4 times!!! I'd have considered myself super generaous to do it once!) and you just can't be making anymore changes so close to the date. You have other things to worry about - I take it they'll know other people at the wedding if their partners don't come?
It's your wedding and nobody has the right to demand anything of you. If you've already invited other people because they told you to go ahead and free up space then that's their own doing, nothing for you to have to rectify.
I don't really think you should get to the stage where you're asking them to pay because it's not about the money really - yes it would incur costs to re-add them in but the principle of the thing is that it's your wedding and there's a lot more than covering the cost of per head food to consider.
Why can't people just have the common sense to know that it is a privilege to be invited to share someone's wedding day, not a right.