[Stooky Bill]

It comes up on occasion that the TV-am building is listed (or something is listed about it) but as that was a relatively new building that only dates from the 1980s so it's not quite old enough I would have thought to qualify for a listing at least, and of course it wasn't the first TV studio in London so it isn't unique enough in that regard.

Listed buildings to be either ridiculously old, cultural and/or noteworthy, and its why you see a lot of castles, churches, libraries (more so Carnegie libraries), older pubs on the list and quite a few things on the English Heritage/National Trust sites.

I dare say if Viacom wanted to they could just knock the whole complex down with a bulldozer and nobody would mind.

The age of most of the building is a lot older than the 1980s. It was a converted garage, Henlys, in fact the BT circuits to and from it were HOG - Henlys Old Garage. 

The age of the building is irrelevant to its listing, there are some from the 80s and 90s
historicengland.org.uk 

TVam wasn't listed but it was/is architecturally interesting as an example of 1980s postmodern architecture. It's nothing to do with its age or what it was used for. The alterations were quite controversial in architectural circles. 
www.architectsjournal.co.uk 

Personally I prefer what's there now, and the eggcups have been kept, I think they come under a conservation area