I'd tweak it slightly with a much more narrow:
Find: <body id="[^"]+" class="calibre">
Replace: <body class="calibre">
Find: html#[^"]+"/>
Replace: html"/>
Those 2 regexes are kind of saying:
- "Hey! Keep going as long as you're NOT a quotation mark!"
It's a little bit safer than .*?, which can sometimes go crazy if you weren't expecting it.