have terrible big trees beside our site edge from old estate next door (the ones with a huge treelined forest either side of their road entrance), after fives years we decided to ask the farmer who turns out hadnt a problem in the world with us touching them, in fact he said we were saving him a job he'd never get around to.
Hired a machine with a huge platform on it for two days and with the help of a driver took half of three trees away.
There is no harm in approaching the owner of the trees as you can only get yes or no......