I finely cut white cabbage and onion. Then grate some carrots. Salt and pepper and a mix of mayo and salad cream to taste. I find just mayo is a bit too sickly.
You can add whatever else you like after that. Raisins, cheese, a touch of garlic.
Shredded cabbage, finely sliced red or white onion, grated carrots...grated pepper, a sprinkle of mustard powder (1/2 tsp) and mix in with mayonnaise. I also add sliced red pepper and raisins sometimes.... maybe some tinned mandarin pieces... celery.... and apple.
If I add fruit, it doesn't last long because the fruit (apple) discolours....
Grated celeriac is also lovely to add to the traditional onion,cabbage and carrots.We make it fresh at work and it has a 7 day shelf life but would go a little longer.It tends to get a little watery.