The biggest house I've done, was a former National Trust property which had been taken over and renovated throughout, with curtains from New York, furniture from all over Europe custom made carpets from UK.
When I got the phone call, it was " Hi, Robert, we are just about to move into the new house, could you come down and give the hall and stairs a clean, they're a bit dusty "
When I got there, the housekeeper showed me around, the total area of the hall an staircase was about half an acre.
The client had spent over a million in the house, but only lived there for a year, making a tactical move to Spain from where they commute once a month to keep an eye on their " business "
Interesting item, was a Union Jack toilet seat in a little office toilet, signed by Gerri Halliwell.