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Hello, welcome to the website. My name isXXXXX can assist you with this.
Do they *need* access to the neighbours land to do the works, or is access a mere convenience?
Okay. Then they can get it, if the purpose is to maintain the premises (i.e. not build new parts to it, such as a conservatory etc...).
They can do this by applying to the Court for an order under the Access to Neighbouring Land Act 1996.
The Court will grant an order usually, and most often, it is something that neighbours agree on when they appreciate the Court is likely to do it anyway. Also, if the neighbour unreasonably refuses, and the application to court has to be made, the Court could order the neighbour to pay the costs associated with the application having to be made. This is why most neighbours try and agree to avoid the costs risk.
Is there anything else you would like me to answer for you?
Of course you can :)
Cutting down a tree might be difficult - again, this could only happen with a court order, but I doubt you're going to get that, unless you can show the tree was placed solely to prevent access.