You know the longer I think about this the less I believe aspects of the passed down history.
Firstly David Lennie was in New Zealand as late as the end of October 1900 as this was when his wife died. -
He wasn't an engineer by trade but a blacksmith /farrier so I dont think he is the David Lennie I had found earlier.
We know he was in Tasmania by 1903 as this is when he remarried. The family story says that he contracted rheumatic fever during the Boer War and married his nurse but I cant find any evidence that his second wife was in fact a nurse during the Boer War .
He remarried under the name McClellan and applied for his WW1 service under the name McClellan and I can find no evidence of someone of either name being part of the contingents leaving from New Zealand .