![Wink ;)](./images/smilies/icon_wink.gif)
Annoyingly, however, both the full timetable (from busmap.org) and the working timetable (from firstlondontimetables.co.uk) only give times at Ruislip Station (obviously, given that's where it starts) and then The Coach & Horses in Ickenham, not for West Ruislip.
Anywho, the basic service frequency is every 15 minutes, with the first bus from Ruislip Station at 0543 (due Uxbridge 0557) and the last bus at 0037 (due Uxbridge 0051). In the other direction, the first bus from Uxbridge is at 0529 (due Ruislip 0542) and the last bus is at 0019 (due Ruislip 0032).
Cheers,
Barry