The latest figures, from the Offender Equalities Annual Report, related to March 2023. In March 2022 there were 162 trans women in male jails and six in female jails. Trans women who have had their new gender legally recognised with a Gender Recognition Certificate (GRC) are not included in the figures. There were 13 prisoners with GRCs, but the report did not specify whether they were trans women or trans men.
https://insidetime.org/newsround/just-5-trans-women-in-womens-jails/