Estate agents and mortgage valuers have two very different ways of looking at a property's potential value.
How can the same property be valued differently?
Agents price on expectation, valuers on comparable sales...
Estate agents have a tendency to use comparables of properties that are on the market, whilst mortgage valuers tend to use comparables of properties that have actually sold. Estate agents will tend to be optimistic with a valuation, whereas valuers are working for the mortgage companies and are therefore protecting the interests of their clients and will tend to be pessimistic - especially in today's market.