Think I fixed it. The error claims "cr_remove_generator_footer_code()" is the cause of it, so I had a look at the code for both plugins and at the bottom they both contain an identical piece of code (with the only difference being the name of the plugin):
add_action('wp_footer', 'cr_remove_generator_footer_code');
function cr_remove_generator_footer_code() {
echo "<!-- WP Remove Generator Meta Tag by Christopher Ross - http://thisismyurl.com -->";
}
Am I right in thinking this code is intended to remove - in this example - "WP Remove Generator Meta Tag by Christopher Ross - http://thisismyurl.com" from the footer of the site? Would it not make more sense to just not include it at all? I removed the above block of code, saved the file then managed to successfully activate the plugin.
This issue also implies that trying to activate any future plugins containing this block of code (substituting plugin/author details) would also be unusable, so just to be safe I've taken your advice and placed the "remove_action('wp_head', 'wp_generator');" variable in the functions.php file of the theme and it works perfectly.
Anyway, thanks for your input Adam :-) And I guess this is now resolved, so if anyone else experiences this issue, either remove the block of code in this post or simply add the
remove_action('wp_head', 'wp_generator');
to your themes functions.php file.