Top Class Comfort Air Conditioning, TCC, not only do split and ducted air conditioning repairs and installation, service and install all models, But they service repair and install all Central Vacume Systems.
This is where I have used TCC they installed a central vacum system, it is brilliant, all you need is the hose attachment and plug in and go for it, our housekeeper loves it. I love it as its silent it really is, you wouldn't know from another room that someone is vacuuming.
They say they service all areas, I assume that's limited to the Sydney area. But they are good and will advise the best way to put in a system. The ideal is obviously to do it when your building I'm sure that would be the smarter more cost effective way, unlike putting it into a completed house, but they do as that's what I had done.

Approximate cost: $Quote