Technically the tree owner only has a duty to ensure their trees are safe and there is no legal restriction on height that trees can grow to.
If you have concerns regarding a tree ask the owner how they intend to maintain it and explain your concerns. You may also be able to cut the overhanging branches back to the boundary yourself under Common Law but you cannot prune the tree’s height without the owner's express permission.
Before either you or the tree owner undertakes works to the trees it is important to check if they are protected by a tree preservation order, or located within a conservation area.
The tree owner is not required or obliged in respect of any law to prune the tree for the benefit of his/her neighbour’s level of light. The only exception might be under the Anti-Social Behaviour Act where the trees are assessed and shown to fall within the definition of a ‘high-hedge’. For further information please visit GOV.UK - hedge height and light loss.