I have received quite a few hits to this blog seeking information about travel arrangements in London over Christmas and the New Year, including those for the Central Line on Boxing Day.
The full tfl (Transport for London) leaflet detailing the arrangements for the holiday period is available here (411kb pdf file).
The Central Line information for Boxing Day, Tuesday 26th December 2006 is:
"Reduced train frequencies on all lines. The first
trains will run through the central area at
approximately 0830. Services finish at Sunday
times. The following exceptions apply to the Central LIne:
no Hainault to Woodford service.
Buckhurst Hill, Chancery Lane, Chigwell,
Fairlop, Grange Hill, Roding Valley,
Ruislip Gardens and Snaresbrook closed."
My research suggests that the first train from West Ruislip to Central London will leave at 08.21 am on Boxing day (and every 15 minutes thereafter). The last direct train from Oxford Circus back towards West Ruislip will leave around 23.38. You could alternatively catch an Ealing Broadway Train 10 minutes later and change at North Acton.
This would then be your absolute last chance of getting back to Hangar Lane, Perivale, Greenford, Northolt, South Ruislip or West Ruislip. As stated above, Ruislip Gardens will be closed all day, but it is a relatively short walk from South Ruislip station.
Warning: Do not bet your life on these times. They have however been obtained from the tfl Journey Planner.