In reply to aostaman:
Although it feels 'right' and so seems shorter/quicker to make an 'East side' start, Gwern Gof Uchaf and the Milestone approach path are almost identical distances from the start of the heather terrace path (It is slightly shorter to access Heather Terrace parking on the road at Glan Dena and walking the direct unmarked path).
The intended descent route makes much more of a difference to the choice of where to park than the HT start.