Passports

Currently the average wait for a new passport is 2 weeks so I think that's cutting it too fine.
You can get your registry office to complete a form that means you can get a passport in your new name before the ceremony, it's just not valid until the wedding has happened.
I've seen some people on Hitched leave their passport until it expires rather than paying for a new one.
I would recommend changing it when you are back and traveling on your maiden name for the honeymoon.

As Hayley said. The only thing I’d add is to make sure all your other travel documents (tickets, insurance etc) are under the same name as will be on your passport.