The plants (we call them zucchinis here in the U.S.) produce both male and female flowers on the same plant. In the last few years (at least here) many of these types of plants have required hand pollination with the lack of bees due to CCD in the bee population (resulting in nearly 60% reduction).
If you're having problems with no female flowers, I can only suggest using different seed source or already started plants next spring. However, it's rather difficult to detect the differences in the new flowers. The male flowers have smaller stems and the females have larger stems and have detectable zucchinis (Oh, O.K., courgettes) developing between the flower and stem. If you have to hand pollinate them, wait until both flowers are fully opened.
At any rate, best of luck next season, which is always the eternal hope amongst gardeners, no?