We check this website, now macmillan.org.uk is up and dont blocked for our system and other users of the Internet.
So, answer to question: Is macmillan Down Right Now? - NO! macmillan is up!
If you have problem with access to site macmillan, and domain macmillan.org.uk is not avalible.
Clear browser cache and/or try other web browser
(Chrome, Firefox or Safari).