INCI: Avena Sativa (Oat) Kernel Flour
Oats milled fine enough to stay suspended in water rather than sinking — that's what "colloidal" means. It's one of the most widely used ingredients in products formulated for dry and sensitive skin, and it has a long history of use.
It's inexpensive, which is why it turns up across every price point. A £4 cream and a £40 cream may both lead with it.
On a label: usually near the top, which means there's a meaningful amount. Watch for: products advertising it on the front where it appears near the very end of the ingredient list — that means there's very little in there.