P8 I am unsure about, Heathrow R3 is dead if Boris gets to be PM. HS2 is a puzzle, if a recession is on the cards they will want to pump funds into infrastructure, particularly in the north where the major voters for Leave complained about being left behind.
I could see HS3 being promoted and HS2 starting from the northern end as a compromise measure, and Boris island being resurrected again.......