XML : Why does my regex work fine on regex101 and rubular but not in notepad++?

I have a regular expression for detecting non ascii characters in some xml.

  [^\x00-\x7F]    

When I test this regex on regex101 or similar website it works as I intend it, picking up non ascii characters.

But when I attempt to use it within notepad++ search function, the regex picks up a lot of characters that should be fine, such as spaces, slashes and quotes.

I have tried it in both ANSI and UTF-8 Formats.

Does Notepad++ handle regex's in some different way? What could I be missing?

Please let me know if you need any more information

Thanks