Once you have copied/pasted, the formulae will reference back to the
original file - imagine this is called company_1.xls, then your
formulae will all have [company_1.xls]'sheet name'!cell_reference in
them.

One easy way to change them to refer to the workbook in which you have
copied them is to highlight all the cells on the graph sheet and use
Edit | Replace (CTRL-H).

Find What? [company_1.xls]
Replace With nothing

"nothing" means leave it blank, then Replace All. Obviously, you should
use the correct filename, and ensure that you include the square
brackets in the Find What field.

Hope this helps.

Pete