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 37min £29. From Heathrow Central Bus Station line 230 bus to Brook Furlong, Milton Keynes Coachway (Milton Keynes Coachway Car Park), bus to Central Milton Keynes, Food Centre (Central Milton Keynes Food Centre B4), then bus to North Gate Bus Station. 2hrs 19min £17. From Heathrow Central Bus Station line 140 bus to Harrow & Wealdstone then train to Northampton. 2hrs 43min £18. From London Heathrow drive to Northampton. 1hrs 10min £13.