Hi LenF,
It would certainly be outside the scope of a mattress forum 
As you mentioned each person can have very different opinions or levels of knowledge about a very complex topic but if for any reason you aren’t comfortable with a particular business then of course it wouldn’t make sense to purchase from them.
I hadn’t seen them before and they don’t list any specific information about their mattresses on their website but hopefully they will provide the information you need when you talk with them. Thanks for the heads up and I’ve added them to the Australian list here.
It’s unlikely that you will be able to find out all the specs you would need to be able to “duplicate” or “approximate” a major brand mattress (see post #2 here)
When you can’t test a mattress in person then the most reliable source of guidance is always a more detailed phone conversation with a knowledgeable and experienced retailer or manufacturer that has your best interests at heart and who can help “talk you through” the specifics of their mattresses and the properties and “feel” of the materials they are using (fast or slow response, resilience, firmness etc) and the options they have available that may be the best “match” for you based on the information you provide them, any local testing you have done or mattresses you have slept on and liked or other mattresses you are considering that they are familiar with, and the “averages” of other customers that are similar to you. They will know more about “matching” their specific mattress designs and firmness levels to different body types, sleeping positions, and preferences (or to other mattresses that they are familiar with) than anyone else.
Since the only way to know for certain or confirm whether any mattress will be a good “match” for you in terms of comfort, firmness, and PPP or how it will compare to another mattress will be based on your own personal experience … if you aren’t confident that an online mattress will be a good match for you then the options you have available after a purchase to exchange or customize the mattress (by rearranging or exchanging layers) and any costs involved or return the mattress for a refund would become a much more important part of the “value” of an online mattress purchase so you can try out the mattress in your bedroom instead of a showroom with the only risk being the cost of returning a mattress if in the worst case, and in spite of the “best efforts” of everyone involved (both you and the retailer you are buying from), the mattress doesn’t turn out to be as suitable a choice as you hoped for.
Phoenix