Changing many cells in Excel to recalculate new values after VAT changes

So you have a spreadsheet with lots of values in – future monthly invoices for service contracts, say. Actual values, not calculations which multiply up by a VAT rate stored in another cell, or a named range, or even as a fixed number in a formula. And the Chancellor of the Exchequer just announced that the VAT rate (sales tax for our colonial cousins) has changed so all your values are now going to be wrong for the next twelve months.

What can you do to change many cells at once by a specific amount?

A few approaches spring to mind, depending on the scale of the problem and the structure of your data.

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