Many people drive or want to drive slightly faster than 70mph on the motorway and if the conditions allow, that should be acceptable to a certain point.
Doubling fines/points around schools would deter many people from speeding around schools, protecting our children. Making residential speeding stricter would benefit many residents and make it safer for children who (rightly or wrongly) play in the street.
Putting the money raised from speed traps back into the road will allow for many repairs (e.g. pot holes) and improvements. It will help reduce the perception that they are just fund raisers/hidden tax.
Cameras shouldn't have to be justified as people shouldn't be speeding in the first place – motorists need to take responsibility for their choice to break the speeding law. Speeding laws are generally seen as a joke and almost everyone ignores them and expects it to be acceptable that it is ignored.