Leylandii is Leylandii - fast growing, light blocking, nutrient robbing monsters which irritate and annoy everyone. Choose Thuja occidentalis 'Smaragd' (also known as Thuja 'Emerald Green') instead. Similar, slower than Leylandii, doesn't get quite so large, but is still too large for the average garden. On the other hand, if you only wanted something that got to, say, 10 feet or less in 10 years (more neighbour friendly), there are plenty of other conifers to choose from. have a look at Thuja plicata 'Zebrina'.