In reply to Emlyn Price:
The best all round guide for winter climbing in the Pyrenees is Pirineos Ascensiones en Mixto Nieve Y Hielo This is also available in French if you don't speak any Spanish.
https://www.libreriadesnivel.com/libros/pirineos-ascensiones-en-mixto-nieve...
Also good if youre specifically in that area is https://www.barrabes.com/en-gb/barrabs-editorial-valle-tena/p-12438
Barrabes have the best stock of guidebooks re the Pyrenees although mostly in Spanish They have more than shown here in their shop in Benasque, along with lots and lots of shiny gear. The guys in the shop are pretty helpful re routes etc if youre in the area.
https://www.barrabes.com/en-gb/shop/search.asp?cSearch=books
If you go much before May you'll almost certainly need skis/snowshoes for the approaches.
The Corredor Estasen on Aneto is an easy scenic gully route to the top of Aneto but best done in Spring. The unmanned huts are really bloody cold, don't underestimate how cold it can get in the Pyrenees.
Post edited at 15:34