Thank-you all for the very informative replies - especially the links
to the refurbishement of the 455s.

From what has been said, it looks like the running of Desiros on the
Hounslow Loop is only temporary, and refurbished 455s will return at
some point. A pity, as I've enjoyed having audible (and readable)
announcments, and the availability of a public lavatory on board (as
was available on slam-door stock) It's been even nicer as First Class
has been declassified for these particular services.

Does anyone know why the 4/8 car stop points were moved down tha
platform (wasting platform length)? Did regulations change, requiring
the stop point to be a set distance from the relevant signal - and
therefore moving the stop point as it's easier (and cheaper) to move
the small square sign than the signal? It may have had something to do
with resignalling work of some kind a few years ago.

Anyway, thanks again for the replies.

Sid