Good choice on the diamonds they are a great snake. I recently bought a pair ($800 for the two of them... goes to show how much pet shops hike up their prices).
You don't need to buy treated wood from anywhere, just go for a walk and pick up some boughs or ask tree loppers in your area - don't collect from national parks etc. Don't need UV. Keep them cooler than most other snakes (I'm in Brisbane and they only get heat from a tiny bulb for a few hours a day, and only because they fed recently. Will be turning i off for good soon) and don't feed as much as other snakes - feed mine once every 3 weeks..
EDIT: sorry didn't notice you'd changed your mind to BHP! Good choice they are lovely snakes but very different