Hi again,
I've found something that might be the son being put on a ship from India back to England. Does anyone have access to the "Bengal Directory 1839" because on the Families in British India Society page, they have that directory as having a record of "master" Coombs on board the "Robert Small" ship sailing Feb 1838 Calcutta to London. If I could see the image rather than just the transcript it might tell me if he's on his own or who his parents are etc? Can't find it on Ancestry. No other records matching that one of an adult at the same time so maybe he travelled alone, going to English boarding school perhaps?