the a 30 from launceston onwards into cornwall has frequent large laybys that are set back from the carrigeway.during the school summer holidays many caravans use these for overnight stops on friday nights and i often see people sat outside having breakfast with aqua rolls all set up etc.the area betwwen launceston and bodmin is a rural area and this practise goes on every year and is safe.alternatively a cl site at tregadillet near launceston is two minutes off the a 30 for a overnight stop.
If you are a member of the Caravan Club,, we stayed at a little CL outside Bovey Tracey called Langaller Farm. It was just off the M5 (on the A38), however you could not hear any motorway noise. It was a fantasitc site and we decided to stay an extra night on our way home as well.
A friend of mine stops off at a pull-in on the A30 near 'Polyphant', although I haven't actually spotted it. It is behind trees, can take 15 or so vans and has a burger/coffee van in the mornings. He has used it many times on the way to St Ives.