In reply to Doug: I completely agree about the datedness of Derek Walker's guidebook. I'm surprised that it's still in print.
I spent a week or so out there last year, as a good friend runs a trekking business out there, and even the local guides weren't fantastic. That, and my level of Spanish is very poor!
There's a reasonable local guide to the 50 best routes in the Valle De Tena, but again, it's in Spanish, and only has drawn (some badly) topos.
I've looked hard on-line for Passages Pyreneens, with no joy, and haven't seen a copy in any of the local shops in Spain.