My neighbours have planted conifers at the other side of my fence. They are growing aggressively.?

Conifers are shallow rooting - they will spread their roots into your garden which could cause you some problems. Also, as the conifers grow and spread their branches, they may damage your fence - depending on the type of fence you have. legally you can't cut anyting not growing in your garden but if the trees are overhanging your garden, then you can cut the overhanging bits. I would try and mention your concerns regarding your fence to the neighbour and if he is not going to play ball, then I would cut a trench along the base of your fence which will cut through the roots of the conifers and seriously damage the trees.