A man dressed up in woman’s clothing…
Approaching a child to talk about underwear / breasts etc…
that is as big a safeguarding red flag as you could imagine.
I would be asking M&S for their safeguarding policy and or reporting that to the police…
It is so far from acceptable that it should be dealt with…
It would be less of an issue if it were a man dressed as a man just offering to find stock etc because the way he dresses sets the expectation of the conversation… a man dressed as a woman clearly sets out an expectation of having a more intimate conversation (as ‘women’ together) which is totally inappropriate.