In reply to The Ghost Rider:
In April, fresh snow can consolidate quite quickly in the strong sun, fluctuating temps and long days. I've had good neve on open slopes and in gullies, deep powder in forests (absolute nightmare). Best bet is to sus out conditions on some easy/smaller peaks first. I haven't climbed Posets but it looks superb by the normal route (from the south). The northern route looks to be a little harder with access to the north ridge by a slanting ramp (could be scary in dodgy snow?).
I was climbing peaks solo generally by their normal routes - still challenging and included climbing and down-climbing grade II winter. Pics in my gallery for Lescun, Gavarnie and Cauterets areas.
Bagneres du Luchon is hopefully next on my places to visit. The peaks on the frontier ridge look pretty good (just north of Benasque).
I've got a collection of books by Basque author Miguel Angulo, called 'Pyrenees 1000 Ascensions'. They're hard to find now, but you might be lucky in Benasque. Great books with very fine sketch maps and detailed route info on all the major peaks of the whole range. If there's a particular route or peak that interests you, I can always scan the relevent section. It's in French but you can always Google Translate it.
Another very useful book is 'Pyrenees Courses Mixtes, Neige et Glace' by Francis Mousel - generally higher grade stuff, but inspiring and all good research.