Leigh,
What I alluded to re David Jason "preventing" repeats do you know if that is quite a common thing how does one actor have that power? I am aware of James Bolam constantly denying repeats of the Likely Lads which led to Rodney Bewes losing lifeline royalties for a number of years and in essence post Likely Lads he has little if no success [Jackanory was probably his only other major "role" ] and was at best a jobbing actor whilst Bolam has played in many shows and probably is on paper quite a rich guy. Ironically though Bolam is still alive That's TV have the show on a loop pretty much .
I'm not sure any performer really has the power to prevent repeats, unless they are a creator, author, producer, (etc.) of the work. Repeats might be withheld as a courtesy to a 'profitable' performer who makes a fuss. Repeats are a cheap way to fill a schedule!
However, the real answer is contracts; historically, relatively few tv shows were repeated, those that were had a single repeat usually within a year of the initial broadcast. Then, often, the tapes were wiped!
Particularly in the early days of tv, actors unions did not want broadcasters to show repeats, treating the recorded work as if it was a single performance that was captured solely for convenient broadcast at a later date. Unions considered a repeat to be an abuse of the performers work unless they were paid again. This harks back to the earliest tv shows that were broadcast live - and repeats were a re-enactment, not a recorded performance.
Furthermore, contracts always specified the number of broadcasts that could be made of the performers' work. This is still true, but now takes into account digital on-demand tv, and streaming via other services like YouTube. Many BBC shows are available for one year (on iPlayer), other broadcasters vary. Contracts also stipulate which platforms can be used for broadcast (tv, laptop, phone, etc.) and also restrict countries that the show can be seen in.
As an example of restricted availability, my "Dry Dock" video contains allowed rights-protected music, but due to contractual restrictions on the music, the video cannot be viewed in certain territories.
The issue is a bit different with Channel 4. Most of their early programming was made by small independent companies that have since merged, been taken over, or ceased to exist. Even if the recordings are still in existence, C4 didn't own many of the programmes - just a licence for a certain number of broadcasts - so couldn't re-broadcast them if they wanted to, as it would be almost impossible to identify the rights-holder.
