I find it a lottery as to what seating style you have on class 377. Is there a definitive list anywhere?
377101-377119 have 2+2 seating throughout. The outer coaches have mainly bay seating with tables. The inner coaches have mainly unidirectional seating.
377120-377139 have 2+2 seating at the outer end of every coach and 3+2 seating in the centre of every coach. Within the 3+2 area, the 3s are mainly in bays. The 2s are mainly unidirectional.
377140-377164 have 2+2 seating in the outer coaches, mainly in bays with tables, and 3+2 seating in the middle coaches
377201-377215 have the same interior as 377140-377164 but are dual voltage
377301-377328 have 2+2 seating throughout but have half tables where applicable.
The change to half tables only happened when they moved to metro work.
377401-377475 and 377501-377523 have a similar layout to 377140-377164 and 377201-377215, but have doors to the first class area and the seats next to the driving cab bulkhead face inwards.
377601-377626 and 377701-377708 have 2+2 seating throughout but most of it is arranged in a unidirectional arrangement, other than at the ends of the carriages.
I think that you are specifically talking about 377/1 - 3 which where designed more as Metro trains, than doing long distance commuter journeys from Brighton to London.
None of them were designed as metro trains. 377/3s started off on the Victoria to Brighton fasts and the Coastway stoppers, and lasted on these duties for some time.
There were never enough 455s and 456s to run all of the metro services. Connex converted the first class areas on 19 VEPs to bench seating to operate metro services in the late 1990s. These were effectively replaced by half of the 377/4 build, which also initially worked East Grinstead diagrams. The carriage working notices of the time identified 377M for Selhurst based units. Later all 377/4s were reallocated to Brighton, with higher numbered 377/1s allocated to Selhurst instead.
Separate 'metro' and 'coast' allocations of the 4-car fleet ended when Southern needed to eek out a bit more availability.