One thing to note, this path assumes the gameinfo.txt has specified the download path (IE "game+download tf/download" in TF2). 

When no download path is specified, folders are created in the root game_info folder (IE modname/user_custom/files) and as a result, this won't find them.

After some investigating, it appears that sprays also assume the download is located in the download/user_custom folder so instead of just fixing these paths, I'm just going to add the download path to the HL2MP example gameinfo. I can't see how it is needed for SP as it's not actually possible to join servers (I believe?).

I assume if you've gotten jingles working then your path is set up correctly but check out 64f7ede00ec56583f35a933796423c69b82c50b8 if you haven't.