Magnolia 'Little Gem'-easily controlled to te 2.5-3m height range that suits your requirements ben. Will generally form a clipped block of foliage over time though not as dense as the lilly pilly we chatted about. *Could be used as a "pleached" hedge(stripping the trunk of foliage and promoting foliage on the top half of the plant) so that a second tier of plant material can be included underneath for a more dynamic visual aesthetic.
Pleached Hornbeam trees - Pleaching is the weaving branches of multiple trees together for privacy, wind & sound block. Best trees for pleaching are Lindens, Hornbeam (Carpinus betulus), Beech, Apple, Pear, Hawthorn, & Carob. The American Hornbeam (Carpinus Caroliniana) is hardy and holds some of it's leaves during winter to provide a privacy screen year round. Because each tree is trained to have a single stem, there is space below a pleached hedge for other plantings (a hedge on stilts!)
Texas Lilac ~ Vitex Blooms all summer long...drought tolerent! Can be grown as a shrub but looks better trimmed as a tree (like the photo). After blooming, shear back (never more than 1/4 of the plant) and it will rebloom and grow vigorously! Love this tree