Jack Taylor wrote:

Would Greenford alone justify the expenditure on continuing
up the old GW Birmingham route? If stations were added at
Park Royal and Hangar Lane then it might help the figures
along and you might as well reinstate a main line platform at
Greenford, rather than remodelling to use the existing LU
platforms, which would probably cost just as much to do
(if not more).

The only problem with reinstatement of Greenford main line platforms is
that they're probably totally unusable, in the same way that the down
island at Princes Risborough became unusable. Unless the platforms were
found to be sound, you would be forced to either completely demolish
and rebuild the station, or move it somewhere else.

In that case, you could argue that you might as well continue
to South Ruislip or West Ruislip, to provide a useful
transport interchange with the Chiltern line, in which case
you might as well continue to High Wycombe - then you're
virtually back in the position that was originally planned
for Crossrail, with a Wycombe branch!

Crossrail doesn't need to go to Wymcobe; if the link line is to be used
at all it should only go as far as Greenford. Interconnecting with the
Ruislips is probably not necessary; both stations are probably
overprovided for as it is. High Wycombe has excellent services anyway
and IMHO the presence of Crossrail on the GW/GC would be unwelcome to
Chiltern. And if Crossrail does make it to Greenford, anyone starting
at the Ruislips will simply take the Central Line to Greenford and
change anyway.