How often can they use the facilty before we can complain? They may use the facility an unlimited number of times until a complaint has been lodged. A single complaint doesn't count. A group complaint will be discounted because it is bullying.
How soon should we lodge a complaint and with whom? The instant a policy is implemented, but not until someone has been attacked. Not with your line manager; and not bypassing your line manager. Definitely not with any staff forum, or with HR.
What's a reasonable length of time to wait for a response? Indefinite, but certainly not less than a year.
Should we challenge any individuals directly? Absolutely forbidden, even - perhaps especially- if the policy mandates doing so before lodging a formal complaint. Direct challenge is harassment. Any formal complaint lodged before a direct challenge has been made can be dismissed for not following proceedure.
What are acceptable words & phrases to use if we do take that route? There are none.
How many women need to make a complaint before it's considered valid? N + 1.
Do we avoid looking directly at him/them? Or do we have to make eye contact? Yes. And also no.
How soon can we leave the room after a man enters, or we find him already there, without it being considered harassment? He must leave first. But you mustn't wait for him to leave.
Simple.