After you set up your Stripe account you can reduce the Stripe fee by informing Stripe of your charitable status. Currently this will reduce the Stripe fee from 1.4% + 20p to 1.2% +20p per transaction.
To do this please email Stripe at firstname.lastname@example.org
Please email them from the email account associated with the Stripe account. The fee will be applied to all users of the Stripe account (ie if you have separate logins, which you should).
I understand that by contacting you our Stripe account can be subjected to lower fees, as the organisation is a charity/non-profit.