As of the 25th May, all organisations, including charities, must comply with the new General Data Protection Regulation (GDPR) law. The ICO have released a new FAQ page specifically to provide small charities with the information you need to comply.
You can have a read of the FAQs here.
Elizabeth Denham, the current Information Commissioner, has also written a blog announcing the Data Protection Act 2018, which sits alongside GDPR. Have a read here to make sure you’re in the know about data protection.