Hello. I am a solicitor with over 15 years experience. I will tr to help. Are you a tenant and if so who is the landlord?
No i own the flat
If the tree is in heir garden (rather than a communal one) then there is very little that you can do. There is no right to light and there will be no legal remedy that you can seek for the blocking of light. However, if your property is caused foreseeable damage by the trees then you might well be able to claim compensation for the cost of repairs. I would suggest you point out your concerns to your neighbour. Any damage caused will now be foreseeable and therefore more likely to be actionable and the neighbour may wish to avoid any future liability.
What to do next depends to a large extent on your relationship with your neighbour. But the short answer is that you will not be able to take any legal action until damage is caused when you could seek compensation and an order requiring remedial work to the trees.