Does anyone remember a children's TV show, where there was a oy and girl, and they travelled to different era's in time. Think there may have been a cave alomg the way. Had a catchy theme tune?

Von, I don't know if you are thinking about a British or U.S. television show. This website lists all the television shows about time travel. Television Shows About Time Travel

The one on the list that appears the closest to what you are describing is a show from 1970 called Timeslip. http://www.imdb.com/title/tt0154091/

If that isn't the show, you should be able to find what you are looking for on the first link in this response. :)

Great site Lemming - I found this on there, maybe this is the one? The Young Jacobites (1960)
Two kids vacationing in Scotland entered a cave and found themselves 200 years earlier in time. They eventually helped Bonnie Prince Charlie escape to France.