These guidelines are on the GOV.UK website.
It's a short item but includes the following:
Searches:
Allow the customer to choose whether they want to be searched by a male or female member of staff. It is never acceptable to search someone to find out their gender.
Toilets:
If a trans person says that a particular toilet is appropriate for them, then that is the appropriate toilet for them.
It is not a trans person’s fault if other people object to them using the toilet they feel is appropriate for them.
A trans person is more likely to be a victim of violence or sexual assault. They are particularly vulnerable to attack and victimisation in toilets.
The article gives a description of trans/transgender, gender identity and non-binary.
It has a statement about the Equality Act 2010:
It is unlawful to refuse a service, or provide a worse standard of service, because a person is intending to undergo, are undergoing, or have undergone gender reassignment. For example, this means that stopping a trans person from using the toilet they feel is appropriate to them may create a risk of legal action being taken against the pub, club or venue you work at.
assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/929624/sia-ds-trans-guide.pdf
These guidelines mean a female security guard must search a male if he states his trans. It also means a security guard cannot ask a male to leave the women's toilets if anyone complains a male is there if he states he is trans.
This cannot be correct with regard to the EA 2010.