https://www.reddit.com/r/transgenderUK/comments/1fenk83/got_invited_to_use_the_ladies_changing_rooms/
"she asked me if I wanted to try them on and invited me into the ladies changing rooms - despite there being a sign saying "women only - all gender changing rooms available downstairs." I definitely don't feel like I am passing"
The complaints form for Primark, is here:
https://www.primark.com/help/s/contactsupport?language=en_GB
If you think complaining is too much - remember - your daughter could be in that changing room, maybe half dressed, whilst a man waves his genitals about behind the curtain next door. And he was invited in.