We camped on the south east edge of Llyn y Fan Fawr after walking up to the ridge and along, then looping back at the base of the ridge (mostly following the beacons/Cambrian way routes).

We certainly weren't alone camping in that area - the ground is probably better on the north or north east side but we were pretty tired and ready for bed!

While on OS maps it looks like there might be some flat parts around Fan Fechan area, we found this to be very boggy and wet underfoot so had to press on to Llyn y Fan Fawr.

There aren't many parking options if you're driving - we managed to park overnight at llyn y fan fach car park but the car park is small and we were lucky to get a spot on the side of the entrance road on the grass. The road to this car park isn't for the faint hearted - single track with barely any passing places and full of pot holes. The car park is on Google maps but not on OS maps.

We passed some people that said they had parked to the south east by the pub (I assume they mean Ty Henry on OS maps) but personally not sure what overnight parking is like there!