The interior in the leading and trailing coaches of 377/140-164,377/2 and 377/4-5 is one of the best in the country. 377101-119 are great throughout. I think the very early /1s have the softest seats of all
377120-139 have the worst interior although unlike 375/9 there are small areas of better seating
377/4-5 have a partition in the leading and trailing coaches as well as having the finalised first class featuring a sliding door plug points and two seats longitudinal
377/3s and 377101 - 119 have a spring under the seat cushions. Why this wasnt in the later 377s nobody knows lol. If i was because of cost then that is very mean.