Thanks for this. I'll do some further experimentation. So far my HDRs are a bit hit and miss. Sometimes, particularly if you select deghosting, I get a very weird rendering with HDR, with some of the tones seemingly inverted. I think that this is because the Leica does not record the aperture used correctly, it's only an estimate and that estimate is not self-consistent on bracketed shots. Since HDR seems to use the Exif data, rather than the exposure values, it produces very strange, unusable, results.
PS: Should I be using the embedded profile or Adobe Standard (on a Leica, that contains its own profiles, which seem similar but different)?