Uxbridge Road to Hayes (actually very near Hillingdon Cycle Track) then take Yeading Lane NOT Hayes bypass (A312) until joining A4180. Follow through Ruislip the pick up signs for Harefield. Distance from South Ken station to Harefield 31Km according to Autoroute.
Hope this helps and it may be slightly more picturesque.
A variant on the routes suggested
Uxbridge Road to Hayes (actually very near Hillingdon Cycle Track) then take Yeading Lane NOT Hayes bypass (A312) until joining A4180. Follow through Ruislip the pick up signs for Harefield. Distance from South Ken station to Harefield 31Km according to Autoroute.
Hope this helps and it may be slightly more picturesque.