Channel 5 is a TV channel in Britain, so named as it was the fifth terrestrial channel - and thus free to watch, not common at the time - in the country. Like other such channels, it broadcasts a variety of general entertainment shows.
It launched in 1997, after a huge media blitz promoting the channel as more modern than the rivals BBC, ITV, and Channel 4, and launched with the Spice Girls singing a rewrite of the song 5-4-3-2-1 (to count up to 5). As Channel 5 was going to use broadcast frequencies that had been allocated to RF outputs from video recorders, a large number of videos had to be returned or fitted with a filter so people could watch.
Channel 5 and Daria
Channel 5 gained the rights to show Daria and debuted it on the 27th September 1997, at 14:30. (Back in the 90s, US shows would not air in the UK for months as channels waited to see what was popular before paying up) Everything but "Is It College Yet?" would be broadcast.
At first it aired in an unnamed block for teens, with Channel 5's children's programming controller saying "Once you get past 13 the last thing you want is to be put into your own zone or slot" - then 5 changed its mind, renaming it The Core and later Milkshake FM (after kid's block Milkshake). Daria ran in all three of these versions, which were all hosted by Kate McIntyre.
A clip of an August 1999 host segment is online, showing Daria getting fanmail ("Daria kicks") - including Daria/Trent shippers! Daria at this point aired around shows as diverse as The Tribe, The Wonder Years, Legendary Adventures of Hercules, and reality show Boyz and Girls (city kids on a Derbyshire farm).
No record remains on whether there was any censorship due to the timeslot, as happened to American reruns on Noggin / The N; as British fans would've learned from Outpost Daria transcripts that lines are missing, and as Daria fans are a mouthy lot, there was probably no cuts.
Channel 5 at Wikipedia
This Is Five on the history of the channel
Channel 5 Launch on Youtube