Have to get to Northam depot somehow, presumably SWT have a few Pompey/Southampton diagrams where no first class is advertised, cheaper than sending them as ECS.
Nope, they run in one of the daily ECS moves from Waterloo or Clapham jn to get to Northam.
They do sometimes escape during disruption though, quite often in fact.
Occasionally they can be coupled up to normal unit(s) on Pompy or Poole services with the normal unit(s) providing the first class.
They are normally used on Waterloo to Windsor, Weybridge, Hounslow, Shepperton (via Richmond) services.
Funnily enough they dont have many more (standard) seats than the ordinary 450s because, although they have had standard seats fitted in the former first class area, they have lost a seat off most of the 3 aside seats in the other coaches to create more standing room.