Since homing in on the LSM as a likely cause of the major drain I've taken to having the battery connected but disconnecting the LSM overnight. Yesterday I checked the voltage at midday, dropped about 0.1v-ish, quite cold for Sussex so a promising figure. Started first turn. Battery charge <14.5 when running. Then did a hardware swap. Switched the LSM from my v6 into the v8, no illumination. Then put the v8 module into the v6 and "let there be light". It would appear a replacement is required. Marinabrian has a recoded unit available for me. It'll be a pleasant surprise if that proves to be the solution. One or two water leaks to trace next.