We have found that using a 4x4" timber on the front and on the back works wonders for a stable footprint. (It also usually reduces back strain!) The machine compresses the wood locally but then it acts as a good damping contact. Shim under the timber to suit your leveling requirements. This set-up also allows for easy movement of the machine when required as a pallet jack will run in between the timbers quite nicely.
As for good holding gear, Kurt vices are among the finest you can buy. (if they're available in Australia.) I have one 4" and three 6" Kurts currently for personal use. At work they hugely dominate as well, both for conventional and CNC use.