There is a dilapidated footbridge to cross at around NM930934 marked on the 1:25k map.
It's a good place to leave the bike as it is not great for cycling after that.
Yes I did exactly that. There is a path through the trees from NM930937 back to the bridge. The ride is very straightforward with just one very short loose section on the return journey which I walked (about 20m!)
From car park to car park in good conditions it took me around 8 hours. Much easier than I was expecting from the WK description!