However, when I go to play a new course there is no tag to tell me what theme it is (unless this is a new addition to the latest update - I hope it is, because it is needed!!). I have to click on a course from the list and wait for it to load in before I even know if I can play it, and with each new theme added this problem just escalates and wastes more of my time. I'm sure people with the DLC don't even realise that so far this is, or has been, the case for the rest of us. 
In the latest update on the PC version (I think it's two days old now?), there is a search filter under "Advanced Search", which allows you to search courses by theme. I tried using it last night to see if a Highlands course was available for play, but it produced no results, probably because no one has published a Highlands course at that time. I think this tool is a great one, but I also think it could be enhanced a bit to narrow your results in more ways... it's a start though.
Oh, and I didn't realize the Highlands theme was added as a freebie to DLC customers either, so my previous comment on this holds less water.