Thanks for all your help everyone, it really shows the ModX community pulls together to get stuff solved. I had a play about with the code and finally realised the following:
&tvFilters=`sitemapexclude==%Include%'
&tvFilters=`sitemapexclude==%Include%`
For some reason I had put in an apostrophe ( ’ ), instead it only seems to work with the slanted apostrophe ( ` ), whatever that is??? I’m not even sure I even have the character on my keyboard (UK)?
Anyway, he ho, its all working as expected so all good
Thanks again to everyone for the help!
Craig