If a colleague refuses to share facilities with you because you're trans, that is their personal discomfort to manage, not your responsibility to accommodate. Research consistently shows that workplace discrimination based on gender identity creates hostile environments that harm both individuals and organisational culture.
Guidelines from equality organisations emphasise that you have the right to use facilities that align with your gender identity, and your employer has a legal duty to support this. The uncomfortable colleague can choose to use facilities at different times if they wish, but they cannot demand your exclusion or differential treatment. Evidence from workplace inclusion studies demonstrates that such exclusionary demands constitute discrimination.
What becomes particularly problematic is when colleagues publicly misgender you or make discriminatory comments about your gender identity. Employment law recognises this behaviour as harassment, and your employer's procedures should address it accordingly. Documentation becomes crucial in these situations, as consistent records help establish patterns of discriminatory behaviour.
Your employer should have harassment procedures in place to address such situations. Speaking to HR or your manager about the discrimination you're experiencing is both your right and an important step in creating accountability. Remember that creating an inclusive workplace benefits everyone, and your presence and dignity matter as much as any colleague's comfort levels.