Well, the walls were easy today. Stupidly. I used, erm, Bloke From Dragonball in the end, destroying all the walls with 30 seconds to spare. No idea how I was going wrong previously.
And now I’m stuck again. I did some more “missions”, killed some people, etc, but I’m on another mission with no idea what to do. Looks like it’ll be back to GameFAQs to read up on what to do this time…