Well, ime surveyors will often value it to what the purchaser of the survey is aiming at, be they the seller of the property or the buyer. We have just sold and had a completely unrealistic valuation on our own and sold for 25,000 less. The purchasers' lenders insisted on their own mortgage valuation and it came in 20,000 less than ours!
don't want to rain on your parade, but many sellers seem deluded in their expectations. <bitter experience!>
you should bear in mind that a mortgage valuation is not for you, its for the lenders. they are looking to find out whether or not they will get their money back if things go tits up, so may (or may not) well be on the conservative side of things. what someone will pay for it another matter, ie. a market valuation, and you dont really know what this is till you have put it in on the market.
Ours came back as exactly what we're paying. However, it was built in the 1950's and last decorated in the 70's so we've got it for £25k less than the other houses locally. We're going to do work on it (so it'll be worth at least £25k more) but I just figure they know what they're doing.....
Thanks all - I'd thought it would probably come in lower than we paid so was pleased it didn't. I just wondered whether they would say if it wasn't worth as much as we were paying, or if they always just sign off the agreed price.