Was in there to today and was very pleased to see the changing rooms are 'women' on one side and 'all genders' on the other. It seems that Primark have been paying attention to women's concerns.
As you turn into the women's area, there's also a big notice up reminding customers that these facilities are women only.
I don't know how well they police this, irl but it is reassuring that expectations are clearly laid out and women can therefore object if men try to access these rooms, in the knowledge the stores own policy will support them.
Other retailers take note! None of you are going doing so well right now that you can afford to make the shopping experience less comfortable for women (who let's face it, are more likely than men to be clothes shopping).