However, the exported file looks OK, but it's impossible to work with - we need "plain data" for further processing, not "good looking".

I attach an example of very simple Report: 

there are totally empty A, B, D, G, I, K, L, M columns;

column F (if longer report, plus other columns, like W, AJ etc.) are merged.

there are totally empty 1, 3, 10, 12 rows and row 4 and row 8 are merged cells and used only for top border to be colored (second row is empty because I deleted our company logo)

number should be formated as numbers (not General), but's not a big deal in newer Office.

I also attach a possible example of "plain" XLS report - how an XLS export could be, to be able to easily use in further work...