Hi Mr G, sorry didn't see your comment before. We walked up from Moel ty Uchaf, via the summit of Pen Bwlch Llandrillo (621m) and then along a vague track that followed the fence line NE from there all the way to Moel Fferna, which was approached principally from the south, then heading NW to the summit cairn. The walk along the fenceline track from Pen Bwlch Llandrillo crossed bogs, into the teeth of a freezing wind and very low visibility. I haven't got round to the fieldnotes yet, but it was a largely miserable experience. I have never, in 14 years+, known G/F to be so angry. The expression on her face when we got to the stile just below Moel Fferna summit was very much one that indicated homicidal tendencies. If you go, I hope you get some clear skies, as I'd love to know what the views are like. :-)
From the top, we retraced our steps south and then took a track heading west (easy walking) that dropped down to the forest above Cynwyd. There's another circle near there (see my recent comment to Postie) that would pay a visit if you have a better day of it. The track eventually hits a road and goes down to Cynwyd village. This would be the easiest line of approach I should think, but if you intend to visit Pen Bwlch Llandrillo as well it's not easy to link them unless you took the route we did. I borrowed it from the Nuttals book.
The Berwyns were nice and sunny looking from Corndon last Friday, it was nice to see what they actually look like! It's very weird to have climbed to such a height but to have no idea what you're on top of looks like. Similar experience to Radnor Forest mountains in fact.