OK thanks. That makes sense now that you have explaned it. And I agree that technically it makes complete sense.
But I think the issue is still there. I have four or five users testing this out for me at the moment and all of them were confused by this. For the user, all they are doing is looking at an identical looking search box and expecting it to work in the same way, wherever they are in the site.
I suppose what I could do is edit the text of the search boxes to reflect this somehow? Not sure what to say exactly though...
Thanks for the help and sorry if I came across as too critical. As I said, I love this tool generally.