From Heathrow Terminals 1-3 train to Paddington Underground Station, Tube to Oxford Circus Underground Station, Tube to London Euston, then train to Northampton. 1hrs 47min £51. From Heathrow Central Bus Station line 724 bus to Watford Junction then train to Northampton. 2hrs 15min £23. From Heathrow Central Bus Station bus to Brook Furlong, Milton Keynes Coachway then bus to Northampton, Coach Park. 2hrs 35min £37. From London Heathrow Airport (LHR) drive to Northampton. 1hrs 10min £16.