Just as an experiment I'd try legacy Excel connector with Custom SQL (see my old post here)
SELECT [DATA$].[ID] AS [ID], [DATA$].[Name] AS [Name] FROM [DATA$] UNION ALL SELECT [DATA$].[ID] AS [ID], [DATA$].[Name] AS [Name] FROM [C:\files\another-file.xlsx].[DATA$] UNION ALL ...
It will probably be just as slow but at least you can fire up extract creation and go get lunch.
Thanks for getting back to me. Can you tell me how I get to the option to
enter a custom SQL statement - I can't see that as an option on the
'Connect .. to a file' screen?
On 22 July 2016 at 09:18, Dmitry Chirkov <firstname.lastname@example.org>