Next door's very large tree

The house next door is owned by someone in the UK. He used to rent it out but its now empty. The trouble is the tree in his front garden. It is that big that our south facing house doesn't get any sun until after 2pm. I have been told that the tiles in his house are starting to crack ( subsidence?) and I don't want that happening to us. I realise that we are allowed to cut back branches and roots but that would be very difficult. Does anyone know who I can contact about this, Ayuntamiento?, as I don't have any contact details for the owner.