Sets are struck a lot quicker than you think. When Strictly was in TC1, is was normal for another programme to be recorded in the studio less than 24 hours later. That wasn't a standing set for the full 10-12 week run (like it is now on half of the George Lucas Stage at Elstree)
I attended an edition of Who Dares Wins in TC1 on a Monday morning a few years ago (well, someone had to) and the previous night, the live results show for that 'How do you solve a problem like Maria' Sound of Music audition show hosted by Graham Norton had come live from it.
In less than 12 hours, the old set had been taken away, and the complex looking set for Who Dares wins (with two soundproof booths, and LED screen, and podiums around 6-8 feet off the floor), studio floor audience seating and a full lighting restrike had been put into place.
Ask most viewers, how long they thought it would take to move on set out and put a new set in, and they'd probably say about a day - not around 9 hours.
My user name might look like Hatton Cross, but it's pronounced Throatwobbler Mangrove.