Reporting bad post codes

I've just reported a handful of bad postcodes, but the process wasn't easy.

I found a whole cluster of CV1 codes, all close together but all miles out, somewhere near Kidderminster. The problem was that it was very difficult to keep track of which ones I'd reported and which ones I hadn't. I've almost certainly missed some, and probably reported some twice. It would be nice if codes that have been reported showed in a nice warning yellow or something.