We have several lists of postcodes in Excel, and they're all in different
formats like below. I've replaced the spaces with underscores.

L9_1AE
L9__1AE
LS9_1AE
LS191AE
L9___1AE
LS9__1AE
LS19_1AE

Without having to go through each and rewrite thousands of post codes, I
want to convert the existing data to a standard format of 8 characters like
the last example and was wondering if anyone had any ideas of formula I could
use to do this.

Thanks for your help in advance!