This is not a "rotation" because high things don't wrap back around. e.g. with offset=13 is is not Rot-13. Instead, it just increases the character value by a certain amount. Some characters might be mapped into unprintable characters.

You know what bob. You're right. I didn't notice it at the time but now it is butt obvious to me. So where is your refactoring then :P

From http://en.wikipedia.org/wiki/Code_refactoring:>

In software engineering, "refactoring" source code means improving it without changing its overall results. The process could be informally referred to as "cleaning up" or "taking out the garbage." Refactoring neither fixes bugs nor adds new functionality, though it might precede either activity. Rather, it improves the understandability of the code, changes its internal structure and design, and removes dead code.

assuming 26 letter alphabet

That should be 'a'.ord, not '0'.ord. Unless you want numbers, as well, but then it's more complicated.