Available 
Bodyshape Ortho Memory Foam Mattress
from £168-£314.
£168-£314
Sizes tracked: Single, Small Double, Double, King Size, Super King
Sleep guide
How to choose the right mattress firmness for your sleep style
Choose mattress firmness by sleep position, body build and comfort preference, then compare firm memory foam examples like Bodyshape and Rock Hard for fit, price and trial terms.
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Last verified: 2026-09-12
What mattress firmness actually means
Firmness is about how a mattress feels when you lie on it, but that feel is not the same as support or pressure relief. There is no single industry-wide firmness rating, so the label on a product page is best treated as a guide rather than a universal scale. In this shortlist, Bodyshape Ortho Memory Foam Mattress (£168-£314), Bodyshape Vitality Memory Foam Ortho Mattress (£189-£359) and Rock Hard Super Firm Foam Mattress (£319-£599) all sit on the firmer end, so the useful comparison is how supportive and contouring each one is likely to feel in practice.
Which firmness suits each sleep position?
Sleep position is one of the clearest ways to narrow the choice. Side sleepers usually need more contouring around the shoulders and hips, so a very firm mattress can feel too rigid unless they know they prefer a solid surface; back sleepers often do better with medium-firm to firm support, while stomach sleepers commonly need a firmer feel to avoid sinking. Because all three example mattresses are already firm memory foam options, the real question is which one matches the sleeper’s position without feeling harsher than they want.
How body weight changes firmness choice
The same mattress can feel different depending on body weight and body shape, so a label alone does not tell the full story. Heavier sleepers may compress the surface more and experience a mattress as softer, while lighter sleepers may feel the same model as firmer and less forgiving. That matters here because the shortlist is tightly grouped: if two people share a bed, the better pick may be the one that balances support and comfort for both rather than the one with the most extreme firmness label.
When to choose a firmer or softer mattress
Choose firmer support if you want a more solid, less enveloping feel, especially for back or stomach sleeping, or if you simply know you dislike a sink-in sensation. Choose more cushioning if pressure relief and surface comfort matter more, particularly for side sleeping or for anyone who prefers a gentler feel from memory foam. With these three MattressOnline examples, the step-up in price from the Bodyshape models to Rock Hard should only matter if the firmer feel, brand positioning, warranty and depth suit the bed and the sleeper better.
What matters most when comparing these mattresses
The strongest shopper takeaway is that firmness is personal, so star ratings matter less than the product details and trial terms when the review volume is thin. In the supplied shortlist, the visible rating averages are 4.5 for Bodyshape Ortho, 4.5 for Bodyshape Vitality and 4.7 for Rock Hard Super Firm Foam Mattress, but the review counts are too limited to lean on heavily. More useful signals are the 100-night comfort trial on all three, the 3-year guarantee shown on the Bodyshape models, and the 10-year warranty on Rock Hard, plus the depth note that mattress height can affect bedding, toppers and bed-frame fit.
How to turn the advice into a shortlist
This is a comparison of three closely related firm memory foam mattresses, not a wide best-buy ranking, so shoppers should choose by fit rather than chasing the firmest label. The price spread runs from about £168 to £599, with five size variants across each model, so first check whether the right size, frame fit and room layout are available before comparing brand or warranty terms. Also verify the live retailer page for the latest price, stock, depth, delivery details and comfort-trial wording, because those practical details can matter more than the star average when review volume is low.
Mattresses to use as comparison examples
Available 
Bodyshape Vitality Memory Foam Ortho Mattress
from £189-£359.
£189-£359
Sizes tracked: Single, Small Double, Double, King Size, Super King
Available 
Rock Hard Super Firm Foam Mattress
from £319-£599.
£319-£599
Sizes tracked: Single, Small Double, Double, King Size, Super King
Retailer details used
Last checked 2026-09-12. The source list below is included to help you check the details behind the comparison. Always confirm the latest price, delivery cost, stock status and product details with the retailer before buying.
- Bodyshape Ortho Memory Foam Mattress | MattressOnlineproduct-page evidence for Bodyshape Ortho Memory Foam Mattress
- Bodyshape Vitality Memory Foam Ortho Mattress | MattressOnlineproduct-page evidence for Bodyshape Vitality Memory Foam Ortho Mattress
- Rock Hard Super Firm Foam Mattress | MattressOnlineproduct-page evidence for Rock Hard Super Firm Foam Mattress
- Mattress Firmness: Finding the Best Firmness for You!Firmness definition, firmness scale, body-weight and sleep-position guidance, pressure/support trade-offs
- Do I Need a Firm or Soft Mattress?Heavier vs lighter sleeper preference, sleep-position summary, couple compromise with medium firmness
- The Most Comfortable Mattress of 2026, Based on Expert TestingPressure relief and support balance, stomach-sleeper firmness framing
Helpful next reads
Use these related mattresses guides and reviews to turn the advice into a practical shortlist.
Firmness questions
Is a medium mattress good for most people?
It can be a sensible starting point, but not a universal answer. Sleep position, body build and personal comfort all affect how a medium feel works, so it is worth comparing it with firmer or softer options if you already know your preference.
Do firmer mattresses help with back support?
A firmer surface can suit shoppers who want a more solid, supportive feel, especially for back or stomach sleeping. It is not a guaranteed fix for comfort issues, so it is better to treat firmness as one part of the decision alongside pressure relief and body shape.
Can two people share the same firmness?
Yes, if their sleep positions and comfort preferences are similar. If one person is a side sleeper and the other wants a firmer surface, the best compromise is often a balanced support feel rather than the most extreme firmness label.
How should side sleepers choose firmness?
Side sleepers usually want more contouring than back or stomach sleepers, because the shoulders and hips need more give. If a side sleeper is looking at these firm memory foam models, they should be especially careful to check whether the firmer feel still leaves enough cushioning for comfort.
Does mattress depth affect bed frame or bedding fit?
Yes. MattressOnline notes that depth can affect suitability for bedding, toppers and bed frames, so it is worth checking the live product page before buying, especially if you use a fitted sheet set, a topper or a low-profile frame.