I did all that, and this bit was the end. I found something, using advanced Google-fu, that basically tells me I have a very limited amount of time in which the service centres are all closed, and I'm to use the biometric services at the Post Office like before. So whew, and I'm glad I'm not making my visa application now, but I'll be curious to see how this affects the future of visa applications here. Will it really be simpler and easier, or only for the UKVI? Only having 60 locations to get biometrics done (with the full application able to be done there at the same time) seems like it would be inconvenient for a lot of people, and be overall inefficient. But this IS the same country that inspired Dickens' Circumlocution Office!