Hi Sean,
 
Thanks for your question.
 
When you see the column referring to body weights you would look at this per person. The reason for this is that you can have a dual tension mattress; Spring tension is determined solely by body weight as this is what provides you the support from inside the mattress. 

Going off your example of 2 individuals weighing 10st; A 10st person would be matched with a Medium spring tension so you would both be fine on the Medium spring throughout the mattress. If one user was 10st and the other 18st then you would need a dual tension mattress; One half Medium for the 10st user and the other half Firm for the 18st user. 
 

 
Always work off it on a per person basis. 
 
Our Artisan 1500 is a medium mattress in the top layers but more the firmer end of medium with a construction 50/50 synthetic and natural fillings. 
 

 
I hope this has answered your questions fully but if you do have any further queries please don't hesitate to contact our office on 0161 437 4419. We are open Monday to Friday 8am to 8pm and Saturday and Sunday 10am to 4pm. 
 
Kind Regards, Lee.