Nah! Having to drag around lots of cash is not better. I went cashless 15 years ago and haven't looked back.
Oh, and chip&pin is quicker and safer if you use it in already developed areas of the world. You can even block your card from being used in certain countries.
The risk calculations have already been done, and it is negligible. There are a lot of better targets in Norway than this bridge/tunnel. There will also be passages between the two sections in an emergency.
UK can vote as much as they'd like. It's EU that decides, and it won't let them just come back after a few years in misery, just because they voted yes now. If they leave, they will be kept outside for years to come.