Please help @ryanc beat some sense in to the UK court system to permit official recognition of their gender https://www.crowdjustice.com/case/non-binary-recognition/
As I understand it the most recent ruling can be summed up as:
"Yes the government discriminated against you, and it would recognise your gender legally if you were British, but because you're foreign it's too haaaaaard 😢"
This is of course a bullshit excuse, but challenging it is expensive.