Women's sports and crime will be the first 2 areas to be rolled back.
With regard to women's prisons UK law is already explicit about exemption from gender reassignment and or sex discrimination, via Schedule 3 [Services and public functions: exceptions], section 27 [Single-sex services] subsection 5b:
(5)The condition is that the service is provided at a place which is, or is part of—
(a) a hospital, or
(b) another establishment for persons requiring special care, supervision or attention.
Prisons are establishments for persons requiring special care, supervision or attention [as are all health services and all premises from which these services are delivered].
Women's rape crisis centres, domestic violence refuges, etc can also make use of this exception. It is worth reading the entirety of Section 27 of Schedule 3: www.legislation.gov.uk/ukpga/2010/15/schedule/3
Further, when it comes to employees in all such services, Equality Act 2010 Schedule 9 comes into play: Work: exceptions
Part 1: Occupational requirements: General
(3) The references in sub-paragraph (1) to a requirement to have a protected characteristic are to be read—
(a) in the case of gender reassignment, as references to a requirement not to be a transsexual person (and section 7(3) is accordingly to be ignored);
This means that all employment situations where female only [ie: women, as defined in UK law] employees are required to deliver services to female only service users [ie: women as defined in UK law] are exempt from any claims of discrimination, provided that any recruitment process is explicit that it is restricted to females only in pursuance of Equality Act 2010, Schedule 3, section 27 [Single sex services] and section 28 [Gender reassignment] and Schedule 9, section 1 [Occupational requirements].