It is generally agreed that a cheaper mattress is a false economy – spending, say, less than £200 is almost certainly not going to ensure you have a restful sleep and wake feeling refreshed, unless you are not using the mattress regularly and are below the average weight.
As cheap mattresses are often thinner and therefore offer less support, they will also need replacing more often - sometimes as frequently as once every two years. The average mattress should last approximately 10 years but this does depend on how you sleep, your body weight and how often you use the mattress.
Your body weight is probably the main factor when choosing the tension you require – the softer ones are better for a lighter person, whereas a firmer mattress will benefit up to a 19 stone person. Many suppliers sell combination mattresses with different tensions on either side, catering for couples with greatly varying weights and preferences, others sell two mattresses zipped together (often called 'zip and link'), and usually there is a flap of fabric covering the link so you cannot feel the divide at all.
With spring mattresses, the firmness is largely dictated by the number of springs. The more springs - the more expensive the mattress will be, but this in turn, will offer greater support.
The visco-elastic foam is designed to eliminate pressure points by spreading body weight evenly. The foam cell mattresses mould to the exact contours of a body, and because they do not harbour dust mites in the same way as more traditional mattresses, they are excellent for asthma sufferers. However, they do tend to harbour heat and moisture easier than standard mattresses so bear that in mind for warmer climates.
Always remember to lie down on a mattress in the shop and don't be afraid to ask for professional advice. Choosing a new mattress is a very important decision and can surprisingly affect a lot more of your health and day to day living than just the time when you are using the mattress. Poor support can lead to all kinds of health issues such as an aching back, shoulders and neck tension problems, as well as pain in the hips and knees.
Make sure the bed base is suitable for your mattress. A tired divan base will make even the most expensive mattress uncomfortable. Divan or upholstered ones are best for spring mattresses as the springs in both components complement each other. Memory foam mattresses are better if you have only a wooden slatted base.