I've never watched it, but it's the same with any of these types of show....they record a series of xx episodes for transmission over a set period of time. When all have shown, they'll repeat episodes from whenever to keep fans of the show happy and to fill odd gaps in the schedule.
Excuse the pun but it’s a bit pointless showing these repeats, fans of the shows watch them continuously so don’t want repeats they would be better just finishing them and show something different, I enjoyed watching the Chase but don’t want repeats.
Because the massive advertising revenue which was once a monopolised by the UK's sole coomercial TV channel ITV is now distributed amongs all the new channels and alternative visual media.