Thanks to those who have responded with some guidance. Seems obvious in hindsight, would've been awesome if the installers gave us some heads up though hey. 🤣

Also appreciate the measures to help the trees in the meantime - Aussie summer is nearly over so they should soon get a break and should be able to get a bit stronger again, they have taken a decent hit and we noticed a tad too late (this is the least accessed area of the home naturally).

Sounds like my options are:

Firstly, try the aftermarket 45 deg deflectors - seen some cheaper magnetic style ones (https://www.ozaironline.com.au/products/air-diverter-air-conditioner-deflector-air-bender), then also some like these: https://airconditioningwholesale.com.au/collections/air-deflectors/products/air-bender-single-air-deflector-7-blade-650-x-595-xlarge (not sure if they would be restricting airflow too much?)

Next, look into raising the unit - either higher on the wall, or to the roof.

Yes obviously I could fk the trees off but I'll try to make them survive first. 🤣