Apart from Winch's book I would suggest:  
"British Economists and the Empire", I and II, Political Science Quarterly,   
Vol. 46, No 2, June 1931 and Vol. 47, No 1, March 1932.  
E.M.Winslow, "Marxian, Liberal and sociological theories of imperialism",   
Journal of Political Economy, Vol. 39, December 1931.  
Also E.G.Wakefield, "England and America", Vol. II, p. 109.  
If you can read spanish I dare to suggest my book on classical economics and   
the colonies, and can give you also a reference of Spanish philosopher   
Ortega y Gasset who endorsed Hegel's views on the former English colonies in   
America.  
  
Carlos Rodriguez Braun