In reply to An Triubhas:
A nice one in Wales, and easily accessible, is to park for Llyn Eigiau and head north at first along a good track to Melynllyn reservoir. A steep little ridge takes you onto the slopes of Carnedd Llewellyn where you'll find a small hut. Leave your sac there while you do the northern tops, then back and over Llewellyn and Yr Elen to drop into Cwm Pen-llafar, where you'll find a bivi boulder below Llech Ddu.
Next day, do the Crib Lem spur (grade 1 or so) onto Carnedd Dafydd. Then an out-and -back to Pen yr Ole Wen. From the Saddle, head for the top of Craig yr Ysfa and back to the car by Pen Llithrig y Wrach.