The following is a list of sites referring to GDPR
Some of these may be touting for business. If they are, that is not why they were chosen to be included in this list. You may find some useful guidance here that relates to your organisation and what you need to do.
I am aware that some of the parent organisations of the charities I support are running training on GDPR and as such you are probably adequately covered for your operations. Others though have no centralised guidance, so are being left to their own devices. Hopefully these links will help, along with other things I have published on this site.
Information Commissioner Site
Probably answers most questions and is a comprehensive plain language guide.
Commercial site offering guidance