00,
P1154 was killed of because it never would have worked! The RN did not want 2 engines, P1154RN was always single engined. They wanted 2 crew because it's job in the FAA was to be a high level interceptor, hardly a good mix with the RAF requirement for a single seat strike attack aircraft.
The RN pulled out of P1154 first when they opted for the McD F-4K, leaving the RAF to struggle along alone with the P1154 until the engine issues convinced even the Ar Staff that it was a non starter.
I was present at the Shoeburyness trials of the plenum chamber equipped Pegasus demonstrator and to your claims of 'serious ground erosion' you have to add the rather more serious problem of serious airframe erosion! It did not work!
P1216 would have gone nowhere for the simple reason that back then NOONE wanted VTOL or even VSTOL apart from a small element in the RAF and the USMC and RN.
I still insist that Claymore was going to be the name for TSR2, Merlin for F111. Incidentally, the TRUE UK potential success story that was scrapped was the P1121, a sort of cross between an F-105 and an F-4. IT was going to be called Hurricane.............