I've looked at it and the GRA in some detail, and it does not ban trans women from women's loos. At the very least, can you confirm you agree with the following:
You are right that the GRA doesn't ban TW from women's loos. The Equality Act does allow for them to be excluded from them though where there is a proportionate means to achieve a legitimate aim. Providing a single sex toilet facility would meet this criteria.
Trans women currently use women's loos
Some do. I've seen some argue against this.
GC people want them to stop.
Not all GC people do. I've seen some argue otherwise.