Mr D wrote:However, i did not know that you could head back out, correct the mistake and finish again.
If you have already downloaded you can't; however, if you realize before then i.e. at or after the finish but before downloading then you can:
BOF Rules:
9.16 A competitor has completed their course after downloading or if pin punches are used, on submission of their “control card”. Competitors are not permitted to return to their course after completion. Competitors must not re-enter the competition area after their race unless the Organiser permits them to do so.