Complex sentence: The Tories saw the Dutch primarily as commercial rivals who, along with the Whigs and their Austrian allies, were keeping Britain in a needless and costly conflict: taxation and the national expenditure was on the increase in England, and demand for goods in decline.
Split into simpler sentences: The Tories saw the Dutch primarily as commercial rivals who, along with the Whigs and their Austrian allies, were keeping Britain in a needless and costly conflict. War taxation and the national expenditure was on the increase in England, and demand for goods in decline.