In reply to hb:
SH575620, or thereabouts. South side of the hill down from the radio mast. Parking for 4-5 cars on the minor road along the side of the lake. It's fairly popular with beginners (the site oi my first lead!!) including the Brenin. Might be worth checking with them if they're using it, in which case it will be swamped, or just get there before 10:00 in which case ou're the incumbant. It's not in any of the guidebooks so far as I know.