Some people think that if they do not provide at the roadside the police will not know if they are over the limit and therefore will “get away” with it. That is not the case, if you fail to provide or obstruct them they will arrest you regardless.
If you are negative on the roadside test they will let you go on your way.
If you are positive they will arrest you and get a specimen at the police station, if that has dropped to below the legal limit they will have to release you without charge.
If you provide over, then you will be charged and bailed to attend court, but that probably would have been the consequence if you just failed to provide in the first place so our advice for dealing with the police if stopped is to co-operate fully and comply with any requests they make even if you think the request is unjustified.