Alistair was born in Tunbridge Wells, Kent, to Peter Appleton and Sally Cooper, their second son. Alistair gained ten O-levels and three A-levels at St. John's Catholic School. In 1988 went to Gonville & Caius College at the University of Cambridge where he studied for a degree in English Literature. Whilst at university, Alistair sang in the chapel choir, rowed for his college boat club, and acted in several productions.

On graduating with a 2.1, Appleton left the UK for Poland, where he taught at the University of Gdansk. He later taught English in Eastern Germany and worked as a translator and journalist for Deutsche Welle TV. Alistair broke into television with Deutsche Welle and eventually became the frontman of the channel's youth current-affairs show, Heat.

In 1999, Alistair returned to the UK, where he scored roles on TV and had an appearance as himself on the 2006 Doctor Who episode Army of Ghosts. He has also hosted several television specials, including The Proms.

Alistair also did some acting, including a role in Footballers' Wives during 2002. In 2005, he completed, The Man Who Drank the Universe, a short documentary on the entheogen ayahuasca. In early January 2007, he appeared in BBC America promos for the fourth series of Cash in the Attic, even though he sat that series out. He currently presents Escape to the Country on BBC One.

Alistair is openly gay, and came out at university. In an article in Gay Times, however, he admits he only fully accepted his sexuality when he lived in Poland and Germany.

In 2000 he converted to Buddhism, and teaches yoga and meditation in the south of England and also on the Holy Isle, his spiritual home.