We explained that we would be gone for two weeks (we're leaving the US on 7/14 and returning on 7/28) and they didn't have any problem with that. We're paying $140 for the entire time. I called 2 places and one was about $240 for the whole time and the second place I called offered the "cruise special" for $140. I've been worrying about this for months and was pleasantly surprised! I don't know if the place we used is a chain but it's called "Formal Affairs."
We're packing the tux and leaving our luggage when we get to London and picking it up the next week on our way to the ship.