Sadly BA needs good hard cash, not an IOU from the one-eyed idiot from north of the border. I think they already have a home for the 757s.
What is needed is a reliable interim solution, ideally with an Airbus or three on which the crews can cut their teethe prior to FSTA. I assume that UK plc is now legally bound by the PFI? If not, can it and buy the hardware.
Any interim solution has to be cheaper than keeping the VC10 in the air for the next 5 years.