My sightings today (Thu 28/11/2013) so far :-
377620 & 377611 At East Croydon on 09:11 to East Grinstead (SU903+904).
377614(iirc) At East Croydon on 09:17 ex Caterham to Victoria (SU907).
3776(21?) Seen as I passed Selhurst depot level with the shed nearest the West Croydon-Norwood lines. It looked like 621 and fits with what Class377/5 says in post 596.
377617 & 377618 At London bridge on 09:59 ex Crystal Palace (SU905+906).
377613 on its own at Norwood Junction on 18:20 to west Croydon (SU901+902).
As I passed Selhurst depot it looked like what may be 621 was there so I later went back North.
377621 alone At Selhurst Depot at 19:25 on the East side of the East most shed at the North end so nearest-to/alongside the West Croydon to Norwood Junction track. Not id-able from Tennison Road bridge as a 456 was in front of it.
377605 I glimpsed approximately in one of the headshunts just South of Norwood junction station. Pretty sure it was 605 but Class377/5s post 599 now makes me wonder where 615 was !.
I then lost my will to live !.
I have updated
my list.
That's 13 in use, 1 at Selhurst so about to be used if not already, 5 at Stewarts lane (on test ?) and 7 yet to be delivered.