According to my councils web site, if the trees/branches are on council land there is nothing you can do. They say that you have no legal right to light.
If branches are overhanging your friends property you can complain to the council, state that they are causing a nuisance and ask that they be pruned back. You can only demand that they be pruned back if they are touching your property.
Alternatively if branches are overhanging your property you can take matters into your own hands, excerising your legal rights, and cut the branches back to your boundary. You have to foot the bill for this and put the cut branches over the boundary as they belong to the council.
I imagine all of this info will be in the FAQ section on your friends council website.