Will the catalytic cleaners help clean the build up in my Big MK10?

Also I am having trouble with my indicator stalk, they sometimes sometimes don't what can I do to resolve this.

 

I don't believe that any Jaguar was ever equipped with a catalytic converter in 1964. Catalysts did not come into play until the 1970s. If you are having performance issues, it is most likely tied to carburetion or engine timing.

Someone else will need to chime in on the directionals, but I know that for the small body sedans of that era, Lucas made a repair kit for the indicator switch.