From Barnstaple bus to Heathrow Airport London. 4hrs 54min £123. From Barnstaple train to Exeter St Davids, train to London Paddington, then train to Heathrow Terminals 1-3. 4hrs 49min £131. From Barnstaple drive to London Heathrow Airport (LHR). 3hrs 16min £45. From Barnstaple towncar to London Heathrow Airport. 3hrs 16min £60.