Looking around the 'net, it seems that it is ridiculously expensive and
difficult to do home-automation in Australia. As we use 240v/50Hz rather
than 110v/60Hz, we can't the US stuff .. which is a pity as it is *much*
cheaper.

That said, does anyone know anything about HA that can help me out
sourcing equipment at good prices.

Here's what I want:
Lighting controllers for four groups of dichroic 'halogens'
    hidden in the ceiling or behind the switch plate is good .. my
    house is being built at the moment, but I wonder if the halogen
    groups will be like our office: power outlets in the ceilings
    into which the transformers are plugged .. if so, I guess an
    appliance controller might work

Lighting controllers for six incandescent lights <= 100W each
Lighting controllers for one 500W flood light
    one again, these would be hidden and I will NOT use inline
    bayonet controllers in the light fittings.

PIR sensors x 5

Sunlight sensor

I'd like all this to eventually come back to an RS-232 port on my linux
box from where I can control everything.

Four of the PIRs will be programmed to turn off lights that have been
left on for a period of no activity and will be wired in series with the
wall-plate switch (ie, light will only come on when there's movement and
the switch is in the on position)

The other PIR will be wired in parallel to the switch and in series to
the sunlight sensor and will turn lights on when people approach the
front door.

I'd prefer all the decision making for the PIRs to be handled by the
computer rather than having it hard-wired so telling you the way I'm
using it is probably irrelevent.

Any help anyone can give me is greatly appreciated. I had thought to go
X10, but that's because it's the system I'd heard of. Other postings to
this group suggest that it might be too outdated. I'm not biased, so
long as it works.

As it's a new house and I'm running lots of CAT6 for ethernet, I'm not
adverse to running extra CAT6 if I need to. Just tell me quick coz the
frame is built and as soon as Christmas break is over the electrician is
moving in :)

Cheers!
Rick Measham