You may have many reasons for wanting or needing to find a new GP practice and there are a number of things you may wish to consider when searching for one. The first is how close the practice is to your home. You can use the NHS 'Find a GP' service to see a selection of practices in your area.
You might want to consider how experienced they are at dealing with trans and non-binary patients. The GP practice you're looking at might be a Pride in Practice accredited service, meaning the practice has put in place additonal training and measures to ensure excellence in LGBT healthcare. You can contact the Pride in Practice team at firstname.lastname@example.org to ask more about a specific practice.
Another route might be to contact trans and non-binary people in your local area to see what their experience has been like. Sometimes, people use local trans groups on social media to reach out to each other, and they may have built up a database of experiences people may have had - both good and bad.
Ultimately the most important element of deciding on a GP is that you feel comfortable there. If you find that you’re being treated poorly, you have every right to make a complaint, or to leave that practice and find another one.