Channel 130 on your Sky remote. No clue what number it is on any other remote.
"SciFi UK presents Firefly weekend, in association with Joss Whedon's Serenity."
(And yeah, that in association thing makes me giggle as well.)
Not only are they showing all the episodes, but each one is intriduced by Joss Whedon, there's interviews and snippets with the cast and little featurettes between episodes.
Looks like my weekend's sorted then...
"Just like the TV show, but... COOLER." ~ Adam Baldwin.