Probably picked the wrong day for this weather-wise but had an enjoyable day out nevertheless.
I decided to follow the route as per the LDWA website so started at SJ195351 - Pont y Meibion, Pandy and went clockwise.
Found parking in a layby at SJ195352. If you turn right out of the layby you'll find a footpath on the right which leads down to the road below, cross the bridge and the start is on the left.
Due to the hot weather forecast (high twenties by the time I finished) I carried 2 litres of water plus snacks. The water was just about enough.
Very quiet trails, only saw a couple of others on foot, some eduro bikes and one group of horseriders and I passed a motorcross event for some entertainment.
I made one silly nav error but retraced my steps. Where the gpx lacked claritiy I did the same as Jon Bowie and copied the dog leg the mixed pair had done.
I've set an nice low bar for anyone else who wants to have a go at this (or for myself if I come back on a cooler day and don't make any nav errors :))