I think this might be my only option, I guess I was hoping to have it all for as little money as possible.  I chose motion detection because the DVR only has a 160Gb drive.  I suppose I could set the other 3 cameras to record 24/7 and switch on the overwrite option.  Motion detection is beginning to annoy me anyway as any brief increase/decrease in brightness (like a cloud passing over) sets all the cameras off.