Just noticed this submission to HS2 by Parsons Brinckerhoff:

http://www.dft.gov.uk/pgr/rail/pi/hi...pdf/oldoak.pdf

see the diagrams and plans on pages 9, 10 and 20 in particular.

As well as a low level Crossrail/Great Western/HS2 station, they
suggest a high level station with:

*four West Coast Main Line platforms (for services either terminating
or going onto the West London Line)
*two Dudding Hill line platforms (so services could be run onto the
Chiltern and Midland Main lines)
*two North London Line platforms (effectively bays facing the Richmond
direction)
*two West London Line platforms