Well not too much done today, I finally got my hands on my new rivnut tool and had a go. I marked up and drilled the holes in the chassis to bolt on the dash/scuttle assembly. Unfortunately, after applying the rivnuts, I found that they stood proud of the surface which pushed all the mounting brackets out of alignment. I sorted this by enlarging the holes in the brackets. Not ideal but it worked.

After this I had another go at the handbrakes, I eventually worked out that there was an piece of the old conduit stuck in the trailing arm. When I knocked this out, it was a relatively simple job to re-assemble the first drum brake, with a new cable. The cables themselves are about twice as long as they need to be, as the locost is only half the size of the original BMW. I'm not sure about the best method to shorten them yet, but I have asked the question on the haynes roadster forum and i'm sure somebody will come up with the answer very soon.