At the risk of encouraging anyone who has even the slightest of connections with the Essex Olleys to announce the fact here rather than actually help you in your search, can I just throw in Charles John Olley who married into my tree in 1887, in Burnham-on-Crouch in Essex? Did he descend from one of the 7 or 8 siblings that you've previously mentioned?
Sorry I can't help you with your original question, however...