Tough question. It is difficult for an individual to take on a council. In the end, public support is needed to make progress, and the public may be apathetic if there is no major issue that concerns them.
Certainly, it is a lot to be said for building a group of like minded people, and a councillor is entitled to hold discussions on local matters with a private group. Ideally, at least some of the group will go a step further and be willing to be candidates for election to the council. If a vacancy arises, it is always possible to force a poll, although there is a cost to this so the impact on public opinion has to be considered.
Provided the challengers to the status quo are careful to stick to facts and to follow the procedures laid down by the legislation (at least so far as they understand them), there should be nothing to fear. Where there is any doubt about the law, the principles I follow are to be honest and to consider whether an action accords with the democratic rights of local people.
Good luck!