Good Morning Liz, 
 
Thanks for your question. 
 
Given what you disclose our advice would be that you would need a level of support from a traditional pocket sprung mattress but with softer top layers so your condition isn't exacerbated. 
 
We would need to know your body weights in order discuss the suitable spring tension as this is determined solely by your body weight. 
 
I would then advise that the best model to look at with ourselves is the Artisan Luxury. This mattress is our softest mattress in the top upholstery giving a luxurious sink in sensation. 
 
We'd recommend trying the mattress by itself for at least 4-6 weeks to get a true feel for it but it could be that you need to a topper as well to introduce an extra comfort layer. This is of course dependent on the severity of your Degenerative Disc Disease. If it does come down to having to add a topper then we'd recommend checking a company online called Soak and Sleep. They have a much wider range of toppers than we do and you should be looking at something like Wool or Microfibres in order to emulate the cool sleep surface of the Artisan range of mattresses. 
 
I hope this has answered your questions fully but if you do have any further queries please don't hesitate to contact us on 0161 437 4419.
 
Kind Regards, Lee.