I managed to scrape together a few minutes last night. The 10mm blue LED for the roof has arrived yet, so I'm hoping it will come at some point today.
I've built everything out on the little breadboards now, including the roof LED (using a temporary substitute) and the speaker, and its all working.
I've only got one WT588D-u to use, so that is still on the original breadboard.
Tomorrow I'll shoot photos of all the components and the assembly process as I fit it in the cardboard box. Real soon now.