Hey, glad this problem is all sorted now, would have posted earlier but been away for a bit. As part of my degree i study property law, party walls, i.e. the fence between the properties here are a huge area of contention and cause loads of problems. Basically, you have to look at the deeds for the property, or the map from the land registry and see whose land it is on, as it isn't an actual wall, you can't both own it. There is only a right to light 'sufficient for normal activities' i.e. you aren't entitled to any more light than you need as a human being, even if you ejoyed a higher level of light before hand. As for the trimming bit, it's a tough one. It is technically their property, even though it overhangs yours. BEst answer is always to ask first! Hope that helps anyone in a similar situation. If you have a specific q, pm me and i'll try t get you an answer.