Hi-5 was a 2008 live-action British kids show, based on the Australian show of the same name. It was hosted by Chris Edgerley, Emma Nowell, Cat Sandion (who would later go on to present CBeebies), Jenny Jones and Luke Roberts. It aired on Cartoonito and CITV in 2008. Unfortunately no full episodes have been found online, however Nos2lgia has uploaded an incomplete version of Episode 1.
UPDATE: The episode 'Fun With Friends' (Season 1 Episode 20) has been found, however it is not allowed to be posted online. The owners of Nos2lgia both have the episode however. It is also confirmed that a few other episodes exist.
UPDATE: A Hi-5 UK YouTube channel has been opened, and has started uploading episodes in two parts. Season 1 Episode 1-20 have currently been uploaded. It is unknown if the channel is official or not as there used to be an official Hi-5 UK YouTube channel a few years ago.
LINK: https://www.youtube.com/channel/UCoFASzyVw31f_Hroc9FkgHw
Hi-5 (UK) Season 1 Episode 1 (Incomplete)