Blimey, most of the time the haggling begins because most buyers want everything and the dog thrown in, not taken out. They are to my mind, pushing it a little bit too much for my liking. They are financially invested though, as they've paid for a survey, so may not walk away to quickly if you don't meet their demands.
The last house I sold, the buyer was a needy demanding idiot. I put it back on the market in the end because he did my head in. I sold again that day and we exchanged contracts the next.