There are plenty of countries where being gay is not even legal, let alone gay people having the same rights to marriage etc as straight people. Stonewall could have turned its campaigning and fund-raising efforts to focus on this rather than supporting a regressive movement that has nothing to do with sexuality.
Plus it isn't like there aren't enough other Trans 'charities' out there.
Mermaids: Supports gender-diverse children, young people, and their families.
Gendered Intelligence: Works to increase understanding of gender diversity and specializes in supporting young trans people.
TransActual: Trans-led organization focused on education, advocacy, and healthcare rights.
GIRES: Gender Identity Research and Education Society provides education and training.
Not A Phase: Focuses on supporting trans+ adults across the UK.
TransUnite: A comprehensive resource for finding local, verified trans support groups.
The Beaumont Society: A national self-help organisation for trans people.
The Clare Project: Peer support for trans/gender-variant individuals.
TransBareAll: Works to improve the health and well-being of trans people.
Sparkle: The National Transgender Charity, facilitating community events and support.
The Good Law Project isn't a charity, it is just a massive grift for Maugham - whom prays on the stupid out there into giving him money for no hope legal challenges.