Must you show disadvantage to a particular group of workers apart from just you?

Not necessarily. It used to be the case that if you could not point to other co-workers who shared the disadvantage, your claim would fail. However, in Eweida and Others v The United Kingdom [2013] IRLR 231, the case of a British Airways check-in operative who was not allowed to wear a visible crucifix at work (see page 169), the ECHR said Ms Eweida was entitled to protection from indirect religious discrimination even though she was the only BA employee affected.