Now my cat is a little bizarre, or thinks he's human, since he actively seeks out a windowsill with a good view of fireworks so that he can enjoy watching them.
However a good friend has a cat who is absolutely terrified and who went missing one year due to hiding.
Nowadays she holds onto a cardboard box for the occasion. She keeps it in the room they'll be in - usually the lounge, behind a sofa. She then covers the box in layers of duvets and blankets - quite a considerable amount of them - and leaves an entrance. She aptly calls it the cat cave. She sprays a bit of feliway pheromone spray inside and leaves a few treats and a bowl of water in there, with litter tray just outside. He stays there the whole night, perfectly happy and safe in the knowledge his humans are near by.