Corrected entry: The British soldiers in the film are seen wearing scarlet red tunics. In reality, the British army in the Sudan wore a more practical khaki uniform, having dispensed with red after the Zulu wars fought nearly twenty years earlier.
Corrected entry: When Harry is in Sudan, his face is mucky, scarred, and he basically looks pretty messy. When he returns he is magically handsome again and doesn't sport any scars or wrinkles.
Correction: If you look closely, Harry only has a few cuts and scratches when he is in prison. Harry is in the middle of the desert, which means it would have taken him some time until he reached a British outpost, despite a harbor. Assuming he left from Egypt (Cairo) to England, which is quite far from the Sudan, it would have taken him several days, if not weeks, until he reached the harbor. As transportation was not as advanced as today's it would have taken him quite a long time until he finally reached England. We can assume it took him several weeks or month until he reached Jacks house. It can be assumed that during that time he had the time to wash himself and the cuts and scratches healed. (Deep cuts leave scars. Lighter scars eventually fade away.)
Correction: This version of the film is in the Sudan 1884 (as in the book by Mason) not 1898, as in the other versions (the re-conquest of the Sudan). The last skirmish by the British army in red was in 1886 at Ginnis. Though the probabilities are that they would have been in khaki, many regiments took their red frock coats to the Sudan, some were worn in combat.