The allegation as to loss of light is without doubt one of the most difficult cases to prove in a Court of Law, and, as Ethel correctly points out above, there is no prescriptive right to light...far easier to prove a "noise nuisance" than a "loss of light". However, don't be deterred in pursuing what you may feel are your rights. Nothing can stop you making a claim through the courts, though be advised that the process may be costly. The end result is a matter of opinion, not a straightforward point of law.
As for the advice given to you by terambulan... be very careful. The solutions offered here may indeed be useful for ending the life of the offending trees, but I would think twice before committing acts of criminal damage.