Valuation of property for mortgage

Hi,

When a valuer is valuing a property for a mortgage, are they using the average of asking prices of similar properties in the same area (i.e. comparables) or are they using what they really think the value is (i.e. asking price minus 10/20% or the amount that a similar property sold for)

What has people's experience been?

K

p.s. not asking about house prices but rather the methodology behind the valuations used

Did anyone get back to you on this?

I posted the same message on boards.ie and got a couple of responses, http://www.boards.ie/vbulletin/showthread.php?t=2056511451

say the asking prices for 3 houses in an estate range from 330 (2 houses) to 450 (1 house) and the price of the same type of house in other estates in the area are 330(ish), and you've agreed a price of 250k for one of the houses where the asking price is 330, approx. what would the valuer put down as a valuation? in the peak these houses sold for btw 600 and 650