Honestly its painful.
When we were selling ours, we spent the whole day, as you said, cleaning, moving things, and presenting the house for the viewing. It was spotless. DH put the dogs in the car and took them out while I stayed to show the couple round.
They turned up and I recognised them straight away, they were a couple that lived in the village who I knew by face but didn't know as such. They turned up with their dog and asked if the garden was secure and could they put the dog on the garden. I told them it WAS secure for our dogs but with theirs being smaller I couldn't guarantee it wouldn't be able to find a way out. They were just like 'oh he will be okay' and left him there wandering around and pissing up everything.
We went inside the house and it was quite clear that they had just come for a nose around and had no intention of buying it. They were just snooping about. They were not listening to me when I was telling them certain things about the house because they just were not interested in that. They were more interested in where I had got my pictures from on the wall in the lounge, and the male of the two was more interested in looking at my DH's bikes and he didn't even go in a couple of the rooms.
I decided to try and wind the viewing up as quickly as I could as I knew there was no way they were buying and it actually felt intrusive with them just wandering round being nosey.
I finally wrapped up the viewing by telling them I had other people on the way to view or I think they would have made themselves at home and put the TV on!
They went outside to get their dog and he had gone! Panic ensued and he started yelling at me that I had told him the garden was secure. I told him that actually I hadn't and he had left his dog in there at his own risk.
After a short time of searching and name calling, the dog was located wandering about in the front garden where he had proceeded to take a shit. I asked them to please pick it up, which they reluctantly did.
They left, thank god, and spoke to my neighbour across the road as they were leaving. When they had gone the neighbour came over to tell me that they admitted to him that they had just arranged the viewing because they liked our house and had always wanted to have a look inside and that they had booked to go to the pub for lunch so would arrange to view it seeing as though they were walking past anyway!
Time wasting morons!