Hi Lynne, 
 
Thanks for your question. 
 
We can do Zip and Link mattresses in our Pocket Sprung range of mattresses (Our Origins and Artisan ranges). The main difference between these range's is that the Artisan range is constructed with natural fillings that provide a cool sleep surface; Ideal for anyone who identifies as a hot sleeper. 
 

 
Spring tension is determined by body weight solely as this is what provides you with the support. As such this will differ between retailers so we'd need to know your body weights to discuss suitability of our own products. 
 

 
Our Artisan Bespoke is the firmest mattress that we manufacture and retail and in the top layers has no sort of sink in sensation whatsoever. This is a model we compare with the Vi-Spring Herald that can be found in stores such as Furniture Village, Harrods, House of Fraser or And So To Bed. 
 
We always advocate testing the comparison models beforehand as we are an online only retailer and our products can't be tested before purchase. However, this is the main reason we have our 60 day love it or return it guarantee; This is a no quibble policy meaning that if the product isn't right it can be returned for a full refund or you can utilise the one time exchange. 
 
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.