I think it does not matter how "parsimonious" is the solution, both solutions have pro's and con's depending on fireman's specific needs. If he needs to process that codes with formulas or codes, he has to be aware that those cells does not contain the entire code, the formulas must add that prefix to the numbers from codes column, this may complicate further formulas.
This problem is solved in mr. Graham Mayor's version, it's a WYSIWYG situation.

But i do believe that VBA must be used only when something cannot be done using built-in tools. And there are lots of tools in excel waiting to be used