Now here's the thing - I've just watched an episode of Dr Who, called Midnight - and it reminds me greatly of an episode of Out of the Unknown from the the late 60s / early 70s!
I remember watching this on the ABC here in Australia. It started out as an SF series and ended up (by season 4) as a Horror series. I still remember episodes like <td align="center"></td> "Level Seven", "Tunnel Under the World", and "Immortality Inc." quite clearly. The series left an impression on me.
Anyway, the episode it reminds me of strongly is "Lambda I", where (according to Time in Advance, which matches up with how I remember it) "...a new form of travel is through the Earth itself via sub-atomic space, known as TAU. The different atomic levels are known as Modes - Gamma, Delta and Epsilon - each more unstable than the previous, the effect on the human mind being so terrifyingly hallucinatory that passengers aboard TAU ships are protected behind "reality shields." A TAU transfer from New York to London goes wrong and the ship is plunged into the feared - but hitherto unproven - Omega Mode."
Both episodes are shipboard dramas where the occupants face the unknown. Despite there being very little "science" in the Dr Who episode, I loved it!
Theme from the series