How do I update the Stripe fees for the portion we pass on to users?

You can update this in the Stripe admin panel:

1. Log in
2. Switch into your organisation account
3. Click 'Finance Admin'
4. Click 'Stripe'
5. Select your Stripe account
6. In the 'Passed On TR Fee Account Code' enter your preferred account code
7. Click 'Update' at the bottom of the page