Moss,
I visited at the end of August and the bog was okay (alright it was at the end of a dry spell). I would have thought that with wellies you should be fine if you go from the NE (footpath at SN111353 from the road - I parked a few hundred metres west from here in a layby by a battered red Polo).
I tried a shortcut back to the road in a NW direction from the stones (like a fool) and found the stream and another bog which was very wet. Don't go to far west from the stones because the undergrowth does hide a few streams.
Good luck.
Grendel