We just "Gazundered" on a �360k property, by asking for a lowered price of �355k due to the survey revealing the need for work on the chimneys.
They both need gallows brackets installed as the chimney breasts have been removed without supporting the remaining structure on some floors.
While it's technically Gazundering, I'd prefer to think of it as haggling for a corrected price.
The process takes so long to complete, that the property can both rise or fall in value. Why should it only be sellers that get to argue the price of a property?
There's always got to be someone who pays more in a capitalist market system. Why should it have to be me?

Factoring in repair work is, in most people's view, quite different to asking for a discount simply because you can.

Regarding your second point, though, the sellers get to argue the price of a property because it belongs to them. Sure, property prices can go up and down during the course of a home sale, but would you consider it fair if a vendor delayed exchange for, say, three months, while you paid for surveys, solicitors etc, and then added �20,000 to the price as a condition of exchange, because the market had moved at that time? When you shake hands on a deal, it's a deal. Or else you need to be very clear that it's just a deal while the market remains at this one particular place.

Ben