As a 45 year-old I am constantly amazed that my 12 year-old son seems unable to even brush his teeth without his headphones on! And I’ve noticed that more and more people wear them in the workplace particularly when undertaking office work. One of my customers had heard (obviously not whilst wearing headphones) that the HSE had banned them.
There are no specific health and safety regulations or HSE guidance that ban the use of headphones in the workplace. Whether they can be worn or not should be identified by Risk Assessment (not necessarily documented unless any significant risk is present). In environments such as warehouses, where staff need to be aware of vehicle movements I would suggest prohibiting their use. In low risk environments such as office there is no real safety grounds.