M&S have responded to people's enquiries, here's one:
https://bsky.app/profile/dpdormouse.bsky.social/post/3lvuzitrplc2f
As expected the staff member was just doing their job, something that happens thousands of times a day in shops all over the country.
As per normal, the trans panic was manufactured.
I fully expect all the GCs and media pundits who were pushing all sorts of hate to apologise, but as a person on their second LGBTQ moral panic I know very well how it goes.