Hi.
After thoroughly reading your website for advice I bought a softer mattress, as neither myself or my partner weigh more than 12 stone and wanted a softer feel, as we mostly sleep on our side. You do say that nowadays people are moving away from advising beds be as firm as they used to advise, and that a firmer bed should not be needed unless you are of generous proportions.
However after a year of the mattress settling, we now have terrible lower back problems. This was not apparent until about a year, which would obviously not fit into any return periods. We are now looking into medium to medium firm. The quest continues.
I just wanted to share this experience, as you website was very very helpful. I only bought fro Litvinoff and Fawcett in Hackney, as I have known them for decades and always bought from them, and they had a sale on surplus stock.