Well, firstly, I’m not sure if ‘we British’ are better than anyone else at being scary, or anything else, as a matter of fact. I have, however, come to accept that we have a certain, unique sense of absurdity to our culture, and strange as it sounds I believe that absurdity has a large influence on what humans find 'scary’.

Absurdity is the irrational. The out of place. It is something familiar in a place it shouldn’t be, or something unfamiliar in the place of something that should be there. In comedy absurdity is especially wonderful because it is unexpected. Non-sequitur humour is priceless because it simply never gets old; it cannot. Drop a whale onto a banana in a skit show; it’s funny without having any particular reason to be, but you can make it even better. Thirty minutes later show a close up of a bunch of bananas, then pull out to show a whole pod of whales falling onto them, but cut away before they hit; it’s hysterical. Drop a banana onto a whale at the end of the show and you’ll probably kill a member of the audience.

Fear can be built up in the same way. Hitchcock himself used it by showing a ridiculously large group of birds sitting on a children’s climbing frame, then a larger group of birds, then a larger one, and a larger one. In one sense the situation is absurd, because it is unfeasible; but it is that displacement from the norm, and the gradual increase of it, that makes it dreadful. It is strange, almost impossible, but we become accustomed to it as a sequence of events and begin to wonder if it is so strange after all. At the same time, we are not given any information about the nature of these birds beyond some slightly dissonant singing as a musical backdrop, and despite this sound being clearly unrelated to the birds themselves we suppose the worst because of it and the build. There is no need for violence or a sudden shock tactic to merit their being scary. Without being explicitly told that these birds are a menace we perceive them as a threat, not a joke. We are afraid of them, not 'despite’ knowing nothing about them, but 'because’ we know nothing about them.

Put a matte, black box the size of a house in the middle of a field. It’s odd. It doesn’t respond to the light properly. It is unnatural in shape and size. It doesn’t fit. Not, perhaps, scary, but it is unsettling. If you own a pet dog, you may have experienced it barking at a new piece of furniture in your house; this is because something that is familiar has not only changed, but has been invaded. There is something new, and, as history and society has (cruelly) emphasized time and time again, people are reluctant to accept change, and this reluctance often manifests as fear.

Leave the box there for a week, we accept the situation.

Move the box to another part of the field with no explanation as to how it got there, it begins to become sinister.

Point out that the shadow of the box does not face the same way as any other shadow in the field, we are afraid.

Change can be scary or funny, gradual or sudden, but it is critical that this change is unexplained for it to be either one. It is often only the timing that separates the two; a practical joke that is badly timed can be greatly distressing to someone, which is why learning the balance is very important for either intent to be achieved correctly.

So, we have learned that placing something strange in a a strange place can be 'odd’. Now, imagine something that has always been familiar, and is in a familiar place, doing something strange. A clock that always chimes on the hour doesn’t do so. A doll on the mantlepiece falls off without any sign of having been disturbed. Your mother has someone else’s voice, but nobody else seems to notice.

This last method in particular can be used to begin a line of thought that a great many people find distressing; that of whether the fault in this event lies outside of the person’s mind, or within it. 'Am I the one who is wrong?’ It brings into question the security of the observer. If the world is suddenly strange, or something strange seems to have happened, but nobody acknowledges this 'change’, it brings forth one of the most primeval of fears; that of one’s own madness. Is there a conspiracy, or is it you who is wrong, are you the one who is the danger to others? Doubt is a very frightening thing, and gradually layering insecurity on top of anxiety is a toxic recipe for a person’s state of mind. The absurdity in this case is not a displacement of something tangible, but of one’s own self; and that is what is so terrifying. There is not only no way for you to be sure of the strange event you have perceived, but of any event you perceive. It is reality itself that has been displaced, and so you are the anomaly; you are the absurdity.

Augh wow shit that is enough TL:DR and I have to go out and gosh there is so much more to be said about this subject but yeah short answer= if you want to learn to make something scary, learn how to make something funny.