Just to follow up:
I've used the Target Ovulaiton test kit, and it works very well. My biggest problem was just to get blood drawn. My vet showed me how, and we did managed one time, but it's not easy. The vet assistant at the veterenarian university in Pretoria (SA) advised me that the larger the breed, the more difficult it is to draw blood, as even though the veins are quite big/bold, they are tough, and when you try to get a needle through, it moves away. So it's rather tricky. But as for the working of the test kit, and the results, it's quite good!