Hi great southern land,
The buckling column gel material ... like all "pure gel" material (rather than gel infused material) is very expensive and it's benefits over other types of premium comfort layers like latex are questionable. While it is certainly durable and pressure relieving ... I doubt I would go there unless there was a clear benefit for using it that justified its expense.
Mattresses that are made of all natural fibers over innersprings (such as cotton, wool, and horsehair over innersprings without any foam at all) are also quite expensive. They require specialized knowledge and construction methods to make correctly which adds considerably to their expense in addition to the fact that these materials are also more expensive than most foam. They are also generally much firmer than mattresses that use foam and in the "reasonably priced" versions are usually not as pressure relieving as mattresses that use high quality foam. They can be excellent quality and very durable but are not as popular because of the difficulty of giving them good pressure relieving qualities and their price.
Once you start looking at mattresses with foam in them ... then latex becomes the material of choice for the criteria you have mentioned (temperature and durability). Your choices would involve latex foam in an appropriate softness level and thickness to provide good pressure relief. This would be over a polyfoam, innerspring, or firmer latex support core. Latex over a pocket coil would be the closest to a "traditional" feel, latex over latex would be the most "premium" version, and latex over high quality polyfoam would be a "budget" choice which would provide much of the benefits of a latex comfort layer at a lower price.
All of these sould have a thick stretch knit ticking to best enhance the natural pressure relieving abilities of latex or a thinner wool quilting in the ticking to add the breathability of wool to the latex (with the tradeoff that the wool may slightly reduce the pressure relieving abilities of latex as it compresses over time). The ticking material should be a natural or semi natural breathable fiber rather than a synthetic.
While an inch or so of polyfoam in the quilting would normally be acceptable ... and would feel softer than wool ... it is a lower cost and quality material and would not be my first choice. I would prefer the use of softer latex or wool quilting rather than having an inch of polyfoam in the quilting but again this would add to the cost of the mattress.
So to recap ... I would be looking for a latex comfort layer ... over an innerspring, latex, or polyfoam support core (depending on your budget and overall preferred feel) with either a quilted cover using wool quilting and a natural or "semi natural" blend (organic cotton or a cotton/bamboo blend are the most common), or a thick stretch knit cover without any quilting.
Some comments on the mattresses you mentioned.
www.simplythebest.com.au/product.php?id=6
I would want to know the layering of the comfort layers in this mattress.
* Natural Latex ... This is great ... as long as the latex is on the top with only the ticking and/or the quilting above it.
* High density hyper soft foam ... depends what they are calling high density. This is polyfoam and would generally be my last choice in a comfort layer unless the polyfoam was a very high quality HR grade or was an HD grade in a lower budget mattress but was firmer (not super soft) and used better construction techniques to make it last longer.
* The New Generation Visco Memory foam ... depends on the density of the memory foam. New generation generally means more breathable memory foam but this is still not as breathable as latex. While memory foam will soften and degrade more quickly than latex ... this is especially true with memory foams that are under 5 lbs. The tradeoff here is that some people like the unique feel of memory foam in a mattress. It is great for pressure relief (its main benefit), but so is softer latex and buckling column gel.
* Cashmere wool ... This is a great material to have in the quilting and/or the ticking as it will help sleep cooler and regulate moisture and temperature.
www.sleepys.com.au/store/Luxury.html
I would also want to know exactly what the layers are in this mattress as well. In particular
Quilt Layers
• Quilting layers of Cashmere Wool and Silk fibres, and Hypersoft foams combine for luxurious cradling comfort
I would want to make sure that the hypersoft foams (polyfoam) was no more than an inch. The cashmere and silk is great if that's all they use (no synthetic fibers).
I'd also make sure that the description isn't missing anything (descriptions will often "forget" to list less desirable materials which is why I would always want to see a spec sheet that describes every layer).
• Wool Blend, Conforma Soft and Pillofoam provides a supportive cushioning effect
Conforma and pillofoam are "words" used for memory foam and/or polyfoam, often zoned in different levels of firmness to match different parts of the body. Remember there are only 3 types of foam, memory foam, latex, and polyfoam. All foams are one of these.
www.sleepys.com.au/store/Spine-Align-300-Mattress-Medium.html
Same comments regarding pillofoam and memory foam used in the mattress.
www.simplythebest.com.au/product.php?id=6
See comments regarding buckling column gel. Used for pressure relief but questionable value compared to other materials which also offer superior pressure relief for most people unless there was a compelling reason to use it based on personal preference or unusual circumstances.
The most common challenges for most people is keeping the hips "up" (they are the heaviest area of the body and tend to sink down too deeply which can put the spine out of alignment) and allowing the shoulders to sink in enough (they are wider than the hips but there is not nearly as much weight in the upper area of the body so they tend to not sink in enough relative to the hips). 5 zoned mattresses are usually a form of what I call "reverse" zoning which puts softer material under the hips rather than firmer material under the hips which shifts the load bearing area of the mattress to the area under the lumbar curve. This can be both uncomfortable for some people and it can also aggravate the tendency of the hips to sink in too far (think of lying on a bar under the waist or the curve of the back while the upper and lower body are allowed to sink down). The theory is that it provides support for the lumbar curve (holds it up) while it provides pressure relief (softer areas) to the bony protrusions of the hips and shoulders. While it can have benefits in certain circumstances and weight distributions, in general having more than 3 zones (firmer under the hips) is not a good "off the shelf" choice unless you have personally confirmed with testing that it works for you.
While I know little about Australian mattress manufacturers, I did do a quick search and there does seem to be some independent factory direct manufacturers in Western Australia including simply the best which you linked to. While they often don't show up high in google searches, a search on "mattress manufacturers western australia" or similar terms (and a willingness to go past the first few pages of search results or to go through various lists which will show up and search the results one by one to see if they are really factory direct manufacturers) will usually result in a few hits.
Phoenix