It's in Scotland, and according to this article it seems he could end up in a women's prison.
Trans rapist who attacked three girls jailed for nine years
For Women Scotland campaigners want to ensure that only biological women are held in women’s prisons. But they believe that guidance allows transgender women there.
Both the Times and the BBC avoid using pronouns for this man, but I was a bit surprised that Rhona Hotchkiss (quoted in the Times) uses female pronouns for him.
It's also good to see the BBC being totally clear about his sex:
... Johnston - a biological male formerly known as David who now identifies as a woman...