I find the most economical are the flat nappies that you fold... depending on the way you fold them they will last from birth to age 2 (and beyond if you have a small child). With the fitted ones they grow out of them PLUS they are more expensive per nappy.

I agree: a combination of cloth during the day and an Aldi disposable at night is the best in terms of economy IMO. And remember if you use a good qulaity laundry powder like Drive or OMO sensitive then you wont need NapiSan.