In reply to Pqhf5kd:
If you continue up the hill past stone farm (away from the reservoir) there is a single flat space big enough for a van on the left. You can walk out the back past the concrete block and through the fields to get to the crag if you want. Just make sure you are completely off the road, its quite tight.
I think the parking at the bottom of the tiny lane belongs to the canoe club, but there were no signs saying don't park overnight. Reckon it would be fine, and quiet.
The carpark directly next to the lake, with the bird hide is very nice (save the local yout doing donuts at 1am) but if you are still there when the warden comes in the morning around 8am, you will get a right earful. Its council owned so they can enforce it.