Seen in service today - 377604/605/606/610/613/614/617/618/619/622/623.
377618 + 623 failed at Wallington with 1633 Sutton - Victoria.
377419 has just led 377625 through Purley on 5G56 Tattenham Corner to Selhurst following a train failure.
www.realtimetrains.co.uk/train/W87870/2013/12/11/advanced
377623 1932 Horsham to London Victoria
377611 2008 Caterham to London Bridge
377609 1936 London Bridge to Caterham (terminated at Purley)
The Horsham service was short formed after the failure of the 1026 Caterham to London Victoria.
I went on to see
377612 2015 Tattenham Corner to London Victoria
377150 2045 Tattenham Corner to London Victoria (should have been 377/6)
377613 2150 London Victoria to Dorking
377615 2220 London Victoria to Dorking (should have been 10-car)
The two observations of 377623 don't tally. Using realtimetrains, and the diagrams on ukmodernemu it looks like there was a swap at Victoria between diagram 610 and 604 with the 1750 to Horsham working out as 5-coach having arrived at Victoria on the 1628 from Epsom Downs.
The 2220 from Victoria to Dorking would have been the same diagram as the failed 1633 Sutton to Victoria. The 1701 from Victoria to Epsom Downs would have been 5-coach as only the 1556 from Dorking arrived in time. The other inbound working for the 1701 to Epsom Downs comes in from Caterham and arrived at Victoria at 1713. This was then available to cover the 1733 to Epsom Downs after the failure at Wallington.
With the 1701 to Epsom Downs only being five coaches, it could only form the 1906 to Epsom Downs on its return to Victoria and the 1915 to Tattenham Corner was subtituted with a four coach 377.
All makes sense now! An interesting set of changes.