Don't recommend the Ecrins. Dead end valley crowded in summer, start point for climbs not so good for satisfying walks. Better alternative centre for walking is Pralognan, many good signposted trails , only drawback huge open camping area. I like the Vercors huge plateau,.south of Grenoble, easy walking. Bit further south, ...I have often stayed at a c.amp.site just above Gap[ and explored the Champsaur, but this is an extra days driving. Briancon is well placed to explore several good areas if you drive out every day. Shorter drive, the area round Lake Annecy has several little peaks around 2,300 metres climbable on good trails. I think that might be my top recommendation, camping Lac Bleu has apartments to rent as well as campsites. Know most alpine areas including Austria, memories of a week of pouring rainŽ! Can answer most .questions.