If I recall, the office is fake, Sugar doesn't have his office in central London, the receptionist is fake (as mentioned above, she's an actress). As for the house, if they don't do tasks each day - I assume not - there's no reason to live there all the time.
Also, a lot of reaction shots on the show can be faked. For example, someone can be saying something and then the editor will find a shot of another person frowning but that may not be a genuine reaction at that moment in time. The editor can alter the reaction shots to make some candidates look worse.