Feature Tree Selection for garden

I would really appreciate help with tree selection. We are looking for a shade tree for the middle of our front garden which already has pencil pines along the boundries. The front is east facing and we are hoping to block out some of the early morning sun. We are looking for an evergreen tree that grows to about 5-7 m that would "blend" with the conifers. The style of the garden is formal but that doesn't necessarily mean we want/need a "formal" tree Roots can't be too invasive as our sewerage lines run across our front garden. That is a list an a half but hopefully there are some ideas out there. Anyone have experience with an Evergreen Ash or a Tuckeroo. I live in Carramar, WA.

Oh no! Not an Ash (Fraxinus Griffithii). Lovely tree, but the roots are quite invasive. I have a row of these guys around 7 years old and they have roots near the top of the soil 2-3 inches in diameter. I wouldn't trust them around any type of water pipe/sewer.
What about a Magnolia Little Gem? Probably slower growing, but have gorgeous white flowers and dark green leaves.

what about a Tipuana Tipu? (sp?)

I like the yellow flowers and they are fast growing.

I was told that councils use them because they don't have invasive roots. My darling mother disagrees. I do see them in a lot of carparks though too.

There is about a trillion threads on this subject loaded with ideas

Fu

Any advice on the Tipuana Tipu? The info I found on the net points to their invasive roots...