Corsa diesels have an oil level light as well as a pressure warning light, so maybe other models do as well.
Once triggered (overenthusiastic cornering, or an emergency stop may do it as the oil sloshes about in the sump) I've had it trigger a couple of times (Turning across a junction with a very sharp camber change, and accelerating up a steep slope).
The lamp stays illuminated until the key is removed. Everything returns to normal on the next journey.