How much can one negotiate when buying a house in London?
I strongly recommend you rent for a while. The London housing market is complex and it will take you some time to get a feel for it. Renting means you will not be in a rush and will make a better decision. Generally you should decide what you think something is worth and offer that, I always ignore the sticker price. A good valuation rule of thumb is to see what the place will rent for and use a multiple of rent roll. Also recent sales information is useful but don’t assume others have not made mistakes so use more than one datapoint.