Historic property rates applied to the subject properties you are looking at which could be cross referenced to the ad’s in the newspapers may also give you some scope on adjusting values in the newspapers to give a firmer guide along the lines of Property A sold for £1,000 in 1935 and had a rateable value of £20, therefore property B with a Rateable value of £30 may have been worth c£1,500; Thoms Directory lists all rateable values and copies are held at the national library. Broad brushstroke but may give some guidance.