A modern equivalent for the old cast iron rainwater goods is "Alumasc", a powdercoated aluminium product. It looks well, resembles the old cast iron and is acceptable for use on conservation projects. It's not cheap but is corrosion resistant and will not require painting for many years. Alternatively "Lindab" do pressed metal rainwater goods, glavanised or powdercoated, and these are very attractive and would certainly be very suitable on a period property. The copper gutters are stunning also, but I wouldn't like to use them on a single storey roof- theft could possibly be a problem.