Almost certainly don't exist any more. This is the kind of thing where you set up a company for the building project, then rip it down afterwards. Sell the ongoing maintenance contract to another company (coincidentally with all the same directors). That way legally speaking any responsibility for building defects discovered later goes up in smoke, and the maintenance company can charge a fortune to fix them as 'out of specification repair'..
PFI/PPI was a political scam, and frankly those in government who resorted to it should be looking at criminal charges themselves.