said for applying for the O-A in your home come IF they sign the certificate BUT it isn't accepted for 2nd year and or subsequent extensions INSIDE of Thailand at immigration offices.
Friday tomorrow. They don't work Saturday or Sunday. You will be lucky if it even arrives there on Monday in time for them to deal with it. You have no chance of getting it back in time by post for Tuesday. I doubt you would get an appointment in time. Last reports are saw were 3-5 weeks to get an appointment after you complete the online application. Even then, it isn't issued the same day. You need to drop off the documents and go back when they tell you. There is no same day service in London. Best to phone a consulate and check if they are actually going to be there. If so, you better get your finger out and get there.
They have replied. The way I am now reading them, I think they may have gone the way of other Embassys and consulates and only issuing visas to bonafide Hong Kong residents only?