I have my own headset, however this does not stop another person sitting in the left hand seat for the next 9 hours with some sort of virus, and 3 hours later another person sitting there for another 9 hours, and so on. Nor does it stop the person on my right bringing something nasty on board and coughing/spluttering in our confined environment. I can see your views regarding the sharing of headsets, which H & S should be aware of. But of course management will not address this due to costs, (unless the HSE say so). A pilots environment does not comply with H & S requirements and it will take a long time for it to do so. However, your concerns do raise an issue and the only way to solve the issue is to bring the matter to the attention of the Health & Safety Executive.