Did Challenge ever have the last series that was originally broadcast on ITV? I've never seen them show the last episode where Bob confirms that it's the end of Blockbusters.
About 100 episodes I think which just went out in a loop - presumably it was one of those situations where an episode starts with three new contestants and the batch handily happens to finish after a third gold run where all new contestants are needed on the next show.
200 odd episodes of that series were made (as by that point the show was effectively on all year round) so quite why they never bought them will remain a mystery. Maybe one day.