I saw this when it originally aired at age 18. I remember it being creepy and made me doubt myself.
On second viewing I found it to still be a good watch. If you take into context of when it aired and who was "presenting" the show there are many clever elements. I grew up watching Sarah Green on Blue Peter, Mike Smith was her long time partner and they were newly married at the time, so this was a nice touch. Michael Parkinson, or "Parky" as he's affectionately known, was a national treasure before the term was coined. Craig Charles was that cheeky bloke from Red Dwarf who first appeared on telly reciting poetry. Overall a heady mix of believability.
I missed this at the time of broadcast for some reason. Catching up with it now having recently enjoyed 'Late Night With the Devil' which has a similar premise. Lots of traits here that have become commonplace to the point of now being over familiar - measuring devices, camera's in rooms catching action and heat sensor camera etc. Great fun spotting the figure of Mr Pipes throughout the show.