Just to answer questions,
"as a family we were all concerned, and I thought about calling the police, but relaly, what would the police do? arrest them for being drunk in charge of a minor?"
The police would check if the child was at any risk, usually by deciding how drunk the adults are, then would ask for a safe relative/friend that the child could be taken to. Then a follow up visit would happen and would add evidence if thre were already concerns registered.
"The thing is, I know that parents can snap. But five or six times a day, ten minutes or more each time? I have wondered about getting them reported - because maybe social services could help with eg parenting classes or similar. Is this naive?"
No, it isn't, children can be a "scapegoat" in a family, whilst many on here will try to tell you that SS will not respond, the chances are that a school/nursery etc may already be expressing concerns and your report will trigger an investigation.
"Ss threshold is so high in some areas due to budget cuts that is bit an indicator as to whether something is worth reporting or not"
Whether a case meets the threasehold, is decided after investigation and there are many other ways of implementing and running a CAF/CIN than just through SS so always report.
This is why Child Abuse/Neglect carries on and gets to the level of children living in dire conditions, because it is ignored by all and by the time SS get involved, an strong attachment is formed to the parent.
This is why the child has to remain in the family, living with a level of Neglect/Abuse, because to remove them would cause more ED than leaving them there.
Even if a parent is having a bad day, there is nothing wrong with someone pulling them upon their behaviour towards their children.
What can start out as "having a bad day" can soon become a normal way of communicating and behaving. I have been guilty of that, after my DH died, i snapped at everyone, it wouldn't have been doing me or my children any good, if it had been allowed to continue.