Thanks Mooh.
(Looks like someone has already used my name there!)
It does not seem practicable to look at every tune listed to see if it has an abc with multi-part guitar tab - I did try a few.

So I still don't have one to use for testing my program - if I make one myself it doesn't prove much!

One reason I wanted to check was that Guitar music is usually written an octave higher than it sounds, so that it can use the Treble Clef.
My program will automatically adjust the Tablature to the correct octave if it knows that you are using a guitar - is this the way that people expect abc files to work as well?

I presume that for other stringed instruments, e.g. mandolin, this adjustment is not necesary?