If the tree owner does not undertake works or provide consent, this may become a civil matter and Council is not the appropriate authority to resolve this problem.
In the first instance you should seek mediation at a Community Justice Centre.
Should mediation not resolve your concerns you should seek advice from the Land and Environment Court NSW.
Legislation titled Trees Act 2006 (Disputes between Neighbours) has been specifically created to enable the Land and Environment Court to adjudicate where a tree on an adjoining land might cause damage or injury to neighbours or to the neighbouring property or where a hedge may cause shading of the neighbouring property. However, the Court cannot make an order unless it is satisfied you have made a reasonable effort to resolve the matter with the tree owner.
For information on support that the NSW Land and Environment Court can provide with trees on neighbouring properties, refer to the NSW Land and Environment Court website.