… a big beer and spirits guide …
A dream job! (Do you know how hot it is here in Holland, right now?)
There are not that many export possibilities out of InDesign for text — plain text, RTF, or, if you tagged your ID file, XML. So it mainly depends on how much you “changed” Excel's column data on merging. For example, if you merged all column data into single lines, you'd need a lot of manual work restoring the proper columns again.
If the text formatting is not important, I think you can best try exporting all to plain text. Add tabs between the original columns, then try if Excel can import tab delimited data. If it does not, replace the tabs with comma's and save as CSV — “Comma Separated Values”. I'm sure Excel can read that.
Some smart preparation in the ID document can help you as well. Is your data now put in a table? “Convert to text” is your friend, inserting tabs and new lines automatically. Unique paragraph or character styles for every (or even “some”) data item? Use that to your advantage to mark as much as you can with search-and-replace.
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