Sally has kindly pointed out to me that there is an example xml report in the Help files that gets close to the answer. (Under Reporting - Reporting overview, halfway down, XML reports link). As it uses Taxon List Key it gives duplicates if names were entered from different lists or with synonyms but I have tweaked it to remove these (around 1400 duplicates out of 15000). I can upload the queries if people think it would be useful.

Gordon

Files added here - http://forums.nbn.org.uk/uploads.php

One is a simple copy of Sally's example in the help file, the second (v2) should group together preferred names across lists.