Comparable mattress to the Relyon Braemar in bespoke size

Can you supply a mattress of this special size, and if so, how much more than the standard double would it be?
I have 'tested' a Relyon 'Balmoral' in our local store (you're probably aware that this mattress has two tier springing) and I found it felt softer than our Braemar (single layer) despite them both being medium, I appreciate there are all sorts of variables involved, but is this a feature of two tier mattresses?
I ask this because I was thinking of your Artisan Bespoke 002 and would have to decide between medium and soft as my wife has always considered the medium Braemar as slightly too hard. but I'm guessing the medium AB002 would be fine for us both.
However convincing her when she cannot try it out for herself will be a problem.
I'm an 80Kilo pensioner and my wife is approx 60 Kilo (actual figure state secret!)
Would appreciate your advice to help us decide.