This is what I am thinking about:
What we want to do is re-establish the principle that single sex services are based on sex
This is what the Equality Act says , but the guidance has been misleading.and doctors have told people they can use opposite sex facilities.
What is needed are clear workable, simple provisions for employers and service providers, that are in line with the Equality Act, don't require them to spend a lot of money and solves the problem for them. Otherwise there is no chance they will do it.
This is the target zone: you need a policy that works on paper, can be enforced in practice, can be communicated to all staff and customers verbally (eg on phone) and is reliable in practice (everyone knows where to go - and it's the same accross branches), and won't get them sued or lambasted in the papers .
Different buildings will have different solutions depending on their size and layout but you want the principles to be the same everywhere.
imagine this conversation "Hi I'm coming to the cinema tonight and I'm a transwoman which toilets should I use"
Staff need to know what to say - the policy needs to be written down and on the website.
If they answer "We respect your gender identity but our toilets are based on sex, you are welcome in our male toilets" , even if there is no violence or harassment the risk is the person turns up and they look like Blaire White or Paris Lees , a customer complains or a staff member might stop them. (And vice versa for a passing transman told to use the ladies) ,,,,a-question-of-consent.net/2020/05/23/the-transman-gotcha/
Or they do with the EHRC advice "you can use facilities in line with your gender identity" and allow in all-comers and give up the ability to challenge anyone. a-question-of-consent.net/2020/08/31/the-authority-that-regulates-security-in-pubs-clubs-says-who-needs-rules-when-it-comes-to-womens-privacy/
So the only workable policy that allows sensible sex based rules to be communicated and enforced is "we have male and female toilets by sex and we have a unisex to anyone"
If a business already has a unisex accessible loo, as most do, it can implement this policy simply. There are 12 m disabled people and estimated 0.5 m. trans so it could have some impact on use and they should monitor.
There is currently no law about who can use an accessible loo and businesses will already tell you this is the policy (and the EHRC does say that gender dysphoria can be considered a disablility). planners consider them multi use (as do the regulations). This would not be a change of rules.
Some larger / newer buildings could also have family, gender neutral etc... options in addition. But if the answer is businesses must build new seperate gender neutral loos accross all branches before you can implement this policy I just don't think they will do it. And I don't see govt mandating a big spend.
......
In practice the place this will play out legally is employers not service providers -- because this is where you have the equivalent of the phone call in advance - the person saying they are transitioning and the business having to have a very explicit policy , and the high risk of being sued.
I think the chance of an employer taking a GC hard line "you must continue to use the gents" particularly if it already had unisex accessible facilities is zero.
So pragmatically what would you tell this employer to do when they face this issue tomorrow ?