National Express services call at Plymouth's bus station. They include the following.
Bristol £13 to £24, three hours, four to six daily
Exeter £7.60 to £12.70, one to 1½ hours, four daily
London £15.50 to £28.20, five to six hours, six daily
Penzance £8, 3¼ hours, five daily
Local services include the following.
Exeter Bus X38 (£7.50, 1¼ hours, six daily Monday to Friday, four on Saturday, two on Sunday).
Totnes Stagecoach Gold (£3.60, one hour, half-hourly Monday to Saturday, hourly on Sunday).
Plymouth sits just south of the A38 dual carriageway, which leads west to Cornwall and east to Exeter (43 miles), where the motorway network starts.
Services include the following.
Bristol £41.90, two hours, two or three hourly
Exeter £9.70, one hour, half-hourly
London Paddington £79.80, 3¼ hours, half-hourly
Penzance £10.70, two hours, half-hourly
Totnes £6.50, 30 minutes, half-hourly to hourly