ok penybryn way up
turn left past old converted chapel and follw fireroad past troedyrhiw farm
this takes you directly to the top of margam mountain
or you can go up the fireroad at craigyaber… after a few hundred yards cross bridge on left and follow track aup left side of valley- more interesting imo head up towards top cross road and you can also follow fireroad to top of margam mount.
just explore from here you can easily drop back down to margam park.