In reply to dsh: The Dyfi hills would be a good one, starting from Aberllefenni, pick up the track at SH 772 100 and follow to SH 774 107, ascend track to SH 767 134, (big climb) and go to Waun-Oer (SH 785 147), Cribin Fawr (SH 800 151), Craig Portas (SH 801 141), Maesglase (SH 822 151), return to Craig Portas and descend via Mynydd Dolgoed (SH 796 137) back to the cars.
We did this it recently was around 15 miles and 3500ft of climbing, did'nt need Ice axe or Crampons at any point along the way. No harm putting an axe in your pack though just in case you felt you needed it.
Good thing about the walk was that you could descend to the start from Craig Portas and not commit to Maesglase if you did'nt want to.
All the best, have a good weekend
Jason