HM Treasury website provides updated details (on a six-monthly basis) of unitary payments on PFI projects overseen by the Department for Transport. This information is available at:
http://www.hm-treasury.gov.uk/documents/public_private_partnerships/ppp_pfi_stats.cfm
The unitary payments are based on outturn prices. On average, the appropriate real discount rate for deriving the present value would be 3.5 per cent., as set out in the Treasury Green Book.
The forecasts of future payments are subject to the performance of the private sector contractors.
The unitary payments represent repayments for the capital value (sum of the capital spend) of the project and will also frequently include inflation, service provision, capital repayments and major refurbishments.