Hi Sand [or should I say "sandgroper" - our national nickname for West Australians for our international members],
Having lived in Perth and also owned a convertible with leather upholstery, I am firmly of the opinion the cloth trim is best suited to Perth however you do not get the heated seat option to the best of my knowledge. If you spend a significant amount of time down South or inland where frosts occur in winter, I would suggest the leather option to get the heated seats.
I was informed by the dealer who sold my partner's car that it is not possible to fit seat covers to the Eos as the side airbags are located in the base of the seat.
Make sure you specify an MY09 specification if you order your car with the diesel engine and DSG transmission to get the common rail and hill-hold features standard on this model. In my opinion, the diesel version would be ideal for Perth from fuel economy and driving conditions perspectives.
I would careful examine whether you need the sat-nav option as the cost of downloading upgraded maps is a consideration especially when compared with alternative portable sat-nav units that can be moved from car to car when needed. Factory sat-nav units fitted to imported cars seem to more prone to false navigation directions than those fitted to locally made vehicles presumably due to time delays in updating the map data for changes.
If you intend doing a lot of night driving outside Perth, I would order the bi-xenon light option - expensive but ideal for kangaroo/wombat spotting.
Naturally you would be aware of the benefits of mud flaps to minimise stone damage to the bodywork. I just wish a pot hole detector option was offered to minimise sidewall damage to the low-profile tyres

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