Here are my thoughts, a free business trip to London and Paris. Can I get a 11-24 L preordered in time? Better check the bank account to see if it is willing to take the hit.

But, I have never been to London or Paris, but every big city that I have been and inside every ornate building I have ever went in to I always end up having to stich if I want to capture the interior the way I want. I like the idea of having the wide lens for those situations.

I would take both lenses (not really I would be checking the bank account). Beyond that figure out a way to carry 14mm in your pocket.