Hi Becky,
 
Thank you for placing your question.
 
The Origins springs/" class="" >Pocket 2000 mattress does have the firm spring tension which is suitable for body weights of up to 20st.  
 
The fact that the mattress is now starting to sag means that it is time to change the mattress.  As you can understand the heavier the sleeper the more stress is put on the mattress which if exceeded causes the mattress to fail, dip or reduces its lifespan. This mattress also has a 3 year guarantee and the fact that your mattress has lasted 5 years plus, is testament to the quality of the construction methods used, which as you know not only gives great support from the spring unit but also great comfort from the upholstery layers.
 
We do now have a range of mattresses suitable for you which are our Resilience mattresses. What we want to offer is not just a bed that ‘will do’ but a bed you’re actually comfortable on and not just a firm slab of heavy weight foam. Whilst you may need to replace a standard bed more frequently than a lighter sleeper, with our dual construction design we can limit the need to replace the entire mattress. Where we differ is we are foam specialists; we can offer a range of high support reflex and PU foams for the support aspect of your mattress. We then match this with a higher density range of hybrid or  Latex using our dual construction method. This means that any wear or sagging that occurs over time can be reduced by having a removable replaceable topper.
 
Our Resilience 1 >mattress is specially designed for the heavier sleeper, offering firmer support and a softer super responsive comfort layer, to ensure the best sleep position.  There is a core mattress for the support plus an additional 7.5cm laygel topper which gives a softer comfort before reaching the firm core mattress.
 
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The Resilience 2 mattress again has a separate core mattress for the support but has a 5cm Latex topper which would then give a more medium comfort allowing you to sink into the topper but without it being overly soft.
 
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I hope the above information is of assistance but if you require further information or advice, please do not hesitate to contact us here at John Ryan by Design on 0161 437 4419. Our small friendly team will be more than happy to assist you.
 
Kind regards Julie