Woofgang:
I've been in Estate Agency & Management for 25 years plus. Anyone can value a house for marketing purposes, you need no qualifications or be a member of a professional body ( though most who work in the big agencies do) Its even easier these days with Rightmove publishing sold prices way back to the late 1990's to find out historical sold prices .
Mortgage valuations are not based on market values done by an Estate Agent, they are based on property value that has to be done by a registered surveyor or valuer, and take into account LTV among other things.
Mortgage companies do not take the word of the Seller, Estate Agent or even historical local pricing when making a firm offer of Mortgage. They always instruct an independent registered valuer/surveyor to do a valuation/survey for Mortgage purposes. This is not to be confused with a 'Survey' that the buyers may initiate themselves for peace of mind that the property they are thinking of buying is habitable and free from major constructional defects.
If you are buying a house with cash then , although strongly advised, it is not obligatory to have any kind of structural survey done.