Here's the relevant bit of The Building (Amendment) (England) Regulations 2024
T1.—(1) Toilet accommodation in buildings other than dwellings—
(a)must consist of—
(i)reasonable provision for male and female single-sex toilets, or
(ii)where space precludes provision of single-sex toilets, universal toilets, and
(b)may consist of universal toilets in addition to single-sex toilets.
“single-sex toilet” means toilet facilities which—
(a)are intended for the exclusive use of persons of the same sex, and
(b)provide washbasins and hand-drying facilities in—
(i)either the toilet room or cubicle, or
(ii)a separate area intended for use only by persons of that sex.
“universal toilet” means toilet facilities which—
(a)are provided in a fully enclosed room which contains a water-closet and washbasin and hand-drying facilities, and
(b)is intended for individual use by persons of either sex.
The Building (Amendment) (England) Regulations 2024
Sorry the formatting isn't great.
I note that it says it refers to Toilet accommodation in buildings other than dwellings - surely that mean pubs etc. are subject to the same regs?
Also that single sex provision is a must, as long as there is enough space, and unisex provision is optional, unless it is the only possibility because of space constraints.
It should not replace single sex toilets as long as there is space for them.
There is no reason to design new buildings which have adequate space for single sex toilets without them, so if there's a trend towards all new building only having unisex toilets, that would appear not to conform to the building regs.
And note that any proposed 'third space unisex toilets' have to be
a fully enclosed room which contains a water-closet and washbasin and hand-drying facilities
so not just any old women's/men's toilet with a fancy new label on the door.