Just like everybody else, you have a right to dignity and safety everywhere you go, including at work. Under UK law, you are protected by the Equality Act (2010), and therefore receive certain protections in the workplace.
No employer can legally discriminate against you based on your trans status - this means that they cannot fire you for coming out, or turn you down for promotions, raises, or other benefits. If you feel as though they have broken this obligation, you should be able to make a formal complaint without fear of repercussion. If you are a member of a trade union, speak to your union rep for some support.
You should also be able to update your name and gender on any relevant documentation without hassle. This includes name tags, email addresses, and human resources profiles.