There is no single fence height that applies everywhere. The permitted height depends on local rules, the location and how open or solid the fence is. A low, open fence may be assessed differently from a tall, solid boundary screen. Check the relevant local requirements before deciding on a height.
Location matters too: a fence beside a property boundary or facing a street may be assessed differently from one within the garden. Consider whether its purpose is to mark a boundary, contain children or pets, or provide privacy, and discuss your plans with neighbours where appropriate. On sloping ground, the fence may need stepped sections or to follow the contours of the land.
