This would obviously depend entirely on the personal circumstances. If someone was so badly injured that moving him would endanger him still further he would obviously be kept in one place until he was fit enough to be moved. If he was wounded less seriously but was hors de combat he might not have top priority to be put on a ship. If he was wounded in some isolated place in the bush it could take days before he could be taken to a port for embarquation. If he was wounded in Natal he would probably leave from Durban, Western Cape, Port Elizabeth, Eastern Cape, Cape Town. If he was right up in the old Transvaal any of them - after two or three days train journey. I think the Union-Castle already had their 14 day schedule, Cape Town to Southampton,(17 days to Durban?) very early in their history but soldiers would have gone on troop ships which were probably slower - and what do you mean by "back to the UK"?, off-loaded at Netley or arrival home?