I can only relate experiences here in US, so I don't know if it fits your area... we have small critters, bigger than a mouse, smaller than a rat, called variously; pocket gophers, ground squirrels or just plain gophers, that produce such holes. Even moles will dig a "back door" to their burrows that can leave such a hole (usually they push up a mound of dirt). Some insects leave holes, but nothing that large... Good luck!