Honest question: Is "because sometimes I need to cut something" a "good reason." I routinely carry a small pocket knife with a 3" blade that folds up, and I use it very frequently. Would this be allowed in the UK?
Also from the site, one of the requirements is "are not lock knives (they do not have a button, spring or catch that you have to use to fold the knife)"
My pocket knife folds open and then catches, meaning I have to push a little metal tab out of the way to fold it back closed. This seems safer to me, since otherwise the blade might fold up on my fingers while I'm trying to use it. Would this be illegal in the UK?
I think those are legal, I think you've got it reversed. Knives that lack some kind of mechanism that locks the blade open are illegal (e.g. a butterfly knife).
Thinking about it, I think that section is to specifically ban butterfly knives. That's the only style of non-fixed blade knife I can think of that doesn't have a compliant locking mechanism.
I got one like that on my keychain too and while the personal at the airport measured the blade size, it was fine to take along for an international flight within the EU. I'm neither from the UK nor a lawyer through, and airport personal aren't the police, still hard to imagine that they'd ignore that if it was illegal.
"It’s also illegal to: carry most knives or any weapons in public without a ‘good reason’"
"A court will decide if you’ve got a good reason to carry a knife or a weapon if you’re charged with carrying it illegally."