A list can be found in the link below , including Greater Western.
http://www.dft.gov.uk/pgr/rail/passenger/invitationtotender/Quote :
"
DfT» Rail Procurement formerly had a settled policy to publish franchise Invitation to Tenders (
ITTs▸ ) once the franchise has commenced and the Public Register Franchise Agreement (PRFA) has been agreed between the relevant Train Operating Company and DfT. Following a review of that policy, in future, subject to the application of any exemptions under the
FOI▸ Act (e.g. commercial prejudice), DfT Rail Procurement now intends to make ITTs publicly available at the same time as the ITT is disclosed to pre qualified bidders."