The NHS gender clinics are VERY reluctant to start HRT before full-time or at least very close to it, they want to see serious commitment ie legal name change, out to friends, family, colleagues with proof.
The private gender clinics are more flexible. Other options also include bridging prescriptions from your GP, though many are reluctant. Or there is the GenderGP service, a private route to bridging HRT.
I don't know your circumstances, but passing has many factors, body movement, shape, face, hair, voice, language, the list goes on. Early on I like many had a very strong desire to pass. I slowly built confidence going out in public that has let me start full-time without HRT, and just get on with my life, not that I'm not keen to get on with HRT ASAP!
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