You should not lose your job because you have come out or plan to transition in the workplace. If you come out and are fired shortly after, this could be considered unlawful dismissal and may be an act of discrimination.
Guidance by The Government Equalities Office recommends that employers have an inclusive environment that welcomes transgender people. If someone decides to transition in the workplace they should be supported by an action plan that addresses dates and timescales, records and systems, pronouns and name changes, making colleagues aware of the situation, facilities, and several other concerns. This is to support the individual and retain them as an employee.
If you feel you have been discriminated against for being trans, speak to a legal advisor confidentially on 08088085678, email firstname.lastname@example.org or online at REE Live Chat.