Help extending a class (Q&A Plugin)

Hi Support.

I'm trying to extend a class used by the Q&A plugin. it's in the file buddypress.php in the folder qa/core/.

I've copied the class code into my theme's functions.php file (it's a child theme) and changed the first line to 'class QA_BuddyPress_new extends QA_BuddyPress {'. I've then just put some test HTML in the block of HTML that starts with '<div id="qa-user-tabs-wrapper...'

Unfortunately when I do this nothing happens, my test HTML doesn't show up, so basically my new class doesn't appear to be extending the old class.

I've looked into object inheritance, but not being a developer I don't understand much about it other than to say that the class doing the extending should be defined after original class. I therefore looked into the order in which the functions.php files are loaded and discovered that child themes load before the parent themes, so that could explain it. I therefore tried loading the new class as an include in 'header.php', but that didn't work either.

Maybe the original class isn't set up so that it can be overridden and I haven't understood the concept, but I've tried everything I can think of and could do with a little help if possible.

All I actually want to do is change some of the HTML output, but as this is 'embedded' in the class I can't think of any other way of doing this, other than to extend the class itself?...

Thanks, Matt