Point of order
In the UK, all debt for which the government is ultimately liable appears as government debt on the national accounts.
If the debt of a PFI company is guaranteed by the taxpayer (as for Metronet, for example, unwisely) then it appears as government debt on the national accounts.
If it does not appear as government debt on the national accounts, that means that the taxpayer isn’t liable for it.
While there are many arguments possible about the benefits or disbenefits of PFI (and, irrespective of whether PFI is a good thing or a bad thing in aggregate, it is certain that the disbenefits are exaggerated and the benefits understated in nearly all discussions of the topic), this isn’t one of them.