Hi, thanks very much for your question. My name's XXXXX XXXXX I'm going to assist you with it.
Unfortunately, there are no statutory provisions controlling the height or overhang of deciduous trees in a neighbouring property (the position is different with evergreen hedges).
Damage that is sustained as a result of a neighbour's tree can be actionable under the law of nuisance. However, in the absence of actual damage, there is little that can be done to reduce tree growth (other than pruning any overhanging branches in accordance with the law of trespass). Any overhanging vegetation which is cut must then be offered back to the owner. Trespass also applies to roots but roots should never be severed without expert advice as this could cause the tree to become unstable.
There is specific legislation governing dangerous trees that can result in action being taken by the local authority (even though the tree is on private land). However, it should be pointed out that this legislation is usually relied on where there is imminent danger or an unreasonably high risk to persons or property. It would not be the right course of action if there is a potential long term danger or there is a perceived possibility of damage if a large tree fell down in high winds.
If the concern is light, there is no general right to light. However, such a right can be acquired in certain circumstances in respect of a particular property or window through which the light enters (known as an easement). Nevertheless, even where this right exists, an infringement to it must be substantial and interfere with reasonable use and enjoyment. This threshold is quite high and would require analysis by a surveyor.
I hope that's helpful but please don't hesitate to let me know if I can clarify anything for you.