The reason the Vanguard that I help to maintain at Brooklands was Grounded in 1996 was lack of spares and engines which neither BAC or Rolls Royce would support any longer so when the Cof A ran out on the 30th September 1996 It wasn't worth trying to renew it at least it didn't end up as Bake bean tins like the other Vanguards.
There's still one (fictitious) Vanguard flying, albeit in Merchantman configuration: