Felled Trees Blocking Access

Can anybody please advise?

I've just been over to check up on my dad's house, and was horrified and very annoyed to discover when we got there that somebody had recently cut down (very badly) 6 large, wild pine trees (they are all on a patch of unused land which is infront of the house). The trees have all been left lying on the track that my dad's house is on, and not only do they look a mess, they are also blocking the two access points to his property and make it look derelict (there's nobody living in it at the moment, but it is still used). 

It was nearly midnight when we got to the house, and the trees were too heavy for my partner and I to move, so we had to try to drive over some of them, and then the next day we had to try to cut off some of the thinner branches and drag some of the lighter trees out of the way, so that we could get our car onto the drive.

The house is the only one along this track, so the fallen trees don't affect access to any other houses.

It is thought that the trees have been cut down because they were blocking the view of the sea of one house in particular which is a little further up the hill from my dad's house, though this hasn't been proven. Many trees have been mysteriously chopped down on this plot and on another plot at the other side of my dad's house over the last year. 

Isn't it illegal to cut down wild trees, and don't you need permission to cut down any trees?  

Can I report this incident to anyone, and if so, who would I need to report it to?  The trees need to be removed before they become a potential fire hazard to the area.