Can I get my neighbours to cut back or reduce the height of their trees or hedge?
In most situations the simple answer to this is no. You have a common law right to prune back parts of a tree or hedge growing over the boundary into your property (subject to any legal restrictions being overcome first such as Tree Preservation Orders or conservation areas) but you cannot compel the owner of the trees or hedge to carry out this work or pay for it. As a general rule you have no legal right to a view which has been obscured by your neighbours trees.
If your neighbours own an evergreen hedge close to your property you can make a formal complaint to your Local Planning Authority (LPA) under the High Hedges legislation as set out in Part 8 of the Antisocial Behaviour Act 2003. There is usually a charge for this and the LPA will consider the complaint using standard government guidance set out in a document called Hedge Height and Light Loss. If your complaint is successful the LPA will determine an Action Height to which the height of the hedge must be reduced.
If your neighbours tree or hedge is dangerous and is a hazard to your property then there is action that can usually be taken. In this situation you should contact an arboricultural consultant for further advice.
It is always better to settle a dispute about trees amicably and it is recommended that you try to resolve it by talking to your neighbours first.