Not a good spot at all. I wanted to go to Paignton via Newton Abbot, since this is the closest stop of the Falcon bus from Bristol Airport. There is very little pavement in any direction, absolutely nowhere for cars to pull over, the curve of the road leaves little visibility when cars are moving slow enough and once they exit the roundabout they accelerate too fast to consider stopping further down the road where there is better visibility. I quickly went back to the bus stop on the roundabout itself since that is the only place cars can stop safely and there is a traffic light just beyond so they have time to consider you. The bus stop is rather limited for cars going in the direction you want: nothing to or from Newton Abbot, cars going to Plymouth from Newton Abbot or Bovey Tracey, or cars going to Bovey Tracey from Exeter. I used the stop to get me out of there ASAP, and was very lucky one of the first cars to pass offered me a lift first to Totnes and then all the way to Paignton.

Space to pullover on the roadside... lots of offers to tamapara and that side road, however none to new Plymouth. Eventually to the ride and hitchiked the lost world highway to Stratford which took eternity.

Best to have a sign indicating EITHER Plymouth (A38) or Bude / Okehampton (A30) and do NOT accept a lift to Exeter services unless you want Exeter

Direction Cornwall: You have to stand on the Grass as there is no shoulder but the road is wide enough for a car to stop to take you; although it is actually not useful to walk that far from Plymouth to catch the same ride

You can reach this roundabout form the St. Erth train or bus stations by a short walk. We got a lift to Plymouth in 20min time.

Bus stop lay-by - no covered shelter. Between traffic lights and pelican crossing. Next to supermarket. Traffic heading from Exeter city center west (A30 - Okehampton, Launceston, Bodmin) and (probably) south (A38 - Plymouth; A380 - Newton Abbot, Totnes). All good for Cornwall.