Hi lacabra,
Unfortunately … I don’t have any knowledge of the UK market so I won’t be able to help in terms of specific retailers or manufacturers I’m aware of there but the brand name of a mattress isn’t particularly important anyway because outside of how suitable a mattress is for you in terms of PPP (Posture and alignment, Pressure relief, and Personal preferences), a mattress is only as good as it’s construction and the type and quality of the materials inside it regardless of the name of the manufacturer and the mattress materials that are used in the UK would generally be the same as the materials in North America (see post #5 here about “brand shopping”).
I would start with the mattress shopping tutorial here because it has the most important information, steps, and guidelines that can help you make the best possible choices no matter which country you live in although you will need to do more of the specific local research yourself about choosing the retailers or manufacturers that you wish to deal with and are more knowledgeable and transparent about the materials in their mattresses. Step #3 of the tutorial has more information about what I would look for and the types of questions to ask them on the phone (before you visit them) when you are deciding which retailers or manufacturers you wish to deal with.
I would avoid trying to predict which mattress is best for you based on specs (either yours or a mattress) or “theory at a distance” and whether a mattress is “progressive” or “differential” or any other design really doesn’t make any difference if it’s a good match for you in terms of PPP and uses good quality materials. The only way to know whether a mattress is a good match for you is either careful testing using the testing guidelines in the tutorial post or if you can’t test a mattress in person then the most effective approach would be a more detailed phone conversation with a knowledgeable and experienced online retailer or manufacturer that can help “talk you through” the options that they offer that would have the best chance of success based on the “averages” of their customers that are similar to you in terms of body type and sleeping style (see mattress firmness/comfort levels in post #2 here). Even the best mattress designers are often surprised at the difference between what a mattress was “supposed” to feel like based on specs and what the mattress feels like in “real life” so I would either focus on what your body tells you when you test mattresses.
I’m also happy to help to the degree I can if you have specific questions about any of the mattresses you come across or the materials inside them them but the same generic guidelines and information would apply in the UK as it does in North America or any other country … and the only difference is that you will need to do more of the research involved in finding the retailers or manufacturers that are transparent about what is in their mattresses and who already know what you would otherwise need to take much more time than you probably have to learn.
You can see some incomplete specs for the Ellastone here. There is more about the different ways that one mattress can “match” another one in post #9 here but Stearns & Foster doesn’t provide the type of specific information about the materials in their mattresses (either now or then) that would be necessary to be able to “approximate it” and even if you were to know it would be very unlikely that you would find another mattress that used exactly the same design, components, and materials in the same layer thicknesses and with the same type of cover anyway so the only practical way to assess whether another mattress feels similar to you would be your own personal testing and experience … not by specs.
Phoenix