Would anyone kindly recommend some software (hopefully freeware) that can assemble a directory of uncompressed YUV data (each component in its own file) into an AVI file? Thanks.
I'm trying to avoid having to write a little software to do this.

Have a look at xnview (www.xnview.com). It's free (I think) and will convert from lots of different YUV formats. You may need to do your job in two stages like YUV to TGA in xnview, and TGA to AVI in Premiere...

Julian