'Greenwich Pensioner' does not necessarily mean he died at the Royal Greenwich Hospital. It just means he had a pension from the Navy. (in the same way that "Chelsea Pensioner" means an army pension). Greenwich refers to the office out of which the pensions were paid. Only if he's listed as being on an 'in pension' would he be in a hospital; most people are on the 'out pension' list
Try posting to the Kent forum, as Gravesend and Greenwich both fall under Kent. (I don't have access to Kent 1841). Include date or year of birth for Elizabeth, and approximate date she married (and who to) as this would really help people looking for them in later censuses!
A Joseph Brown m. a Sarah Spooner 30 Mar 1807 at St. Alphage, Greenwich, Kent. Gravesend baptisms are on the IGI until 1812 but can't spot Sarah - was she born after this? I do see two children, one Elizabeth in 1815 and one John James in 1822, christened in Woolwich to a Joseph and Sarah but who knows if they're yours.
