Grobert, you are mostly on the right path. The short answer is that, Yes, you can use XHHW-2 stranded wire for your internal control panel wiring. AS/NZS 3000 pretty much is the primary standard for use in situations such as this.
I'm assuming that your control panel is not going into an underground coal mine. If it is, then there are a WHOLE BUNCH of additional standards that the panel must comply with depending on which state the panel is going into.
I used to live and work in Australia from 1996 to 2000, and here are some excerpts from a general electrical specification that our company used to procure equipment...
Control Wiring
1)All control circuit conductors for voltages up to and including 660 Volts shall be a minimum of 7/0.50mm (1.5mm2) stranded, tinned copper V90 0.6/1kV single insulated cable.
2)PLC or microprocessor I/O wiring shall be stranded, V90, 0.6/1kV, tinned copper conductor with a minimum size of 7/0.37mm (0.75mm2).
3)All control circuit conductors for voltages above 660 Volts but not exceeding 1200 Volts ( 1000 VAC Nominal ) shall be a minimum of 7/0.50mm (1.5mm2) 1kV/1kV stranded, tinned copper V90 insulated and sheathed cable.
4)All wiring shall be oil resistant.
5)Intrinsically safe wiring shall be carried out strictly in accordance with AS/NZS 2380 - Part 7, particularly regarding the provisions detailing the segregation of intrinsically safe and non-intrinsically safe conductors. Intrinsically safe wiring shall be in earth screened cable with a light blue outer sheath.
COLOUR CODING
1)All wiring shall be colour coded as follows:
a) AC Power
Phase 1 Red[/red]
Phase 2 White
Phase 3 Blue[/blue]
Neutrals Black
b)DC Power
Positive Red[/red]
Negative Black
c) Control
32VAC or less:
Active Brown
Return Brown /Yellow
32 to 250VAC:
Active White
Return White/Blue
110VDC or less & PLC Digital I/O:
Active Orange
Return Orange /Black
PLC analog I/O & Process Control:
Positive Grey
Negative Grey/Black
d) Earth & Earth Screens: Green /Yellow
e) Intrinsically Safe:
Light Blue Sheath
Screen Clear
Positive Blue
Negative Black
Hope this helps. If you want more details just ask.