In the light of the statement from KLPA can as many members/swimmers as possible write to them to say they have been misinformed as to their rights and obligations under the Equality Act 2010, and that you would like an explanation of why they have not invoked the exemption (Equality Act 2010, Schedule 3, Part 7, Paragraph 28) that is available to them and that would have permitted the Pond to remain single-sex without any contravention of Equalities law.
You might also want to add your own experiences of the pond, and why it remaining single-sex is important to you.
You might also want to ask how they will differentiate between legitimate and illegitimate claims of womanhood made by males, and what liability the association would accept in the cases of voyeurism or other improper intrusions.
You might also want to note the lack of consultation and the apparent complete failure to get independent advice etc
Sadly I am not a member or user of the pond, so can't write 'as a member/swimmer', though will write as a concerned member of the public. However, it will be the members/users letters that count.
Send letters to Co-chairs, Julia Dick and Nicky Mayhew c/o [email protected]