The below link will take you to the National Online Safety website where you can download a wide variety of guides.
You can also find information from NSPCC and O2 via the following links:
This page allows you to search for apps, social media sites etc to get the latest information and guidance. It is updated regularly.
This page has all the information about the partnership between NSPCC and O2. The tools and tips section has lot of useful information and there is information on a helpline for parents at the bottom of the page.