I remember watching Timeslip as a nine-year-old kid in 1970. I would rush home from school always eager to see the next episode of Simon and Liz as the went through time barrier into future or past alternate worlds. I seem to recall one in a strange Ice Age future.
At first, Simon, who looks like a young youth version of Rolf Harris, is a bit of a geek, while Liz is more adventurous and reckless. This causes arguments, but as the show and stories go on; Simon and Liz become much more confident in each other's abilities. The theme tune was rather haunting too and is very retro 1970s.
Timeslip was a British children's science fiction tv show which is often focused on scientific abuse and Eco damage of our world.