Hello and thank you for your question. I will be very pleased to assist you. I'm a practising lawyer in England with over 10 years experience.
May I clarify please is the tree just a single tree or is more than one tree forming a small hedge of 2 or more trees please?
Is the tree actually planted on the neighbours property and grows out of their land?
Does the tree interfere with light entering through any of your windows and if so have those windows been in place for more than 20 years?