Sorry, but a property is worth what someone is willing to pay for it. If you had 3 surveyors round from different companies, they would value the property at 3 different prices.
Who told you that the property s worth only �225,000? If an Estate Agent still has them selling for �239,000 then presumably that is what they are worth.
A building society may also have just asked for a 'drive by' survey to take place. They would therefore have asked the surveyor if the price is sensible and in line with current prices. If there were no comparables at the time, then the surveyor could easily have agreed with the higher price.