Yes and one could argue those things are an infringement on personal freedoms and should be avoided. I'm not sure if it's actually unconstitutional in the UK, however.

As far as the US is concerned, there's the possibility of martial law but it's well regulated by the fact that the citizenry is extremely well armed and they generally know it's not a good idea to do it, let along maintain it too long, without legitimizing reasons.

There's a delicate balance to it, sometimes restrictions via martial law are actually legitimate and it's a good idea. Imo that's best regulated by having a dangerous populace like the US has. It's a hard thing to argue when the restrictions are too much, so the best course of action is to have it subject to the will of the people, and backed by arms.