Hu Mac
As others have said LPG can be expensive for heating but it is dependant on the type of heating. Also don't be fooled by natural gas being cheaper as the service costs charged can wind up the cost.
For heating you may want to consider Hydronic heating rather than a ducted central heating system, ( I assume that is what you meant by central heating).
This form of heating is pleasant and can be in every room of the house. For a retro fit to an exist house you require sub floor access so a slab house is not possible, however with a new build slab you can incorporate both radiators and underfloor heating.
Have a look at this company as this is who I would buy gear through when I did hydronic heating jobs.
http://www.huntheat.com.auYou can use the water heating unit for your domestic hot water use as well on some models.
Your idea of a larger bottle with refilling onsite can be beneficial if the gas supplier offers a discounted price. As a gas fitter (not on the tools these days) I use to do a lot of large installations,residential and commercial, for 2 suppliers and am aware that they did offer discounts on large users. This worked on expected gas usage which you can work out via the appliance mj/hr rating. On our house we recently moved from in the Blue Mts we relied on gas and it worked for us. Here in Qld I have fitted an LPG Rinnai HWS and will fit gas cooking, however heating is by way of tracky dacs!
There is a lot to consider especially if you can consider supplementary forms of energy to assist like solar boosted water or wet back heaters.
Good luck with the move
