Neighbours

I really wouldn't say anything. Cannabis use is very common especially on the street where I live and although it is illegal and the police are unlikely to do anything as it is a class B drug...

Unless it’s in the driver MissA - that could be a problem

It's not legal, but some police forces will do nothing.
Some may confiscate it, and that's it, and very few would see it as a big deal.

I think the main concern here is drug driving. If the driver abstains and the children are happy and cared for - no problem.
Driving under the influence - problem

I wouldn’t like it. Is cannabis legal here ?

Your only option is to report them for smoking cannabis, but I don't think the Police would take any notice. In any case, would it really be worth it - assuming you don't want to make enemies of them. Personally I'd leave things as they are. They're not hurting anyone, are they? Live and let live I'd say.

It is a a difficult one. Some neighbours may smoke cigarettes outside their homes or drink to excess and make lots of noise. It depends how often they do it and how long it goes on for. No I would not like it but not sure what if anything I could do.

Nothing.

No. Whether they smoke cannabis or not is nothing to do with you.