The power cars were almost identical to the second and third batches of Class 116. The differences were:

a) train vacuum pipes hung vertically down at the front of 125s as opposed to projecting forward on 116s (there were however two exceptions to this in the form of 50988 and 51154).

b) two windscreen wipers were carried on each driving car of a 125 as opposed to the original one each end on a 116, later 116s were fitted with two each end.

c) only one MU jumper cable was fitted to a 125 on the opposite side to that of the two fitted to 116s.

d) the Orange Star coupling code symbol, rather than the more usual Blue Square was displayed on the extreme lower corners of each cab front.

The trailers were also very similar to those of the 116 with little to identify them except that of their interior bulkhead which dictated slightly different bulkhead window positions between the two types. (In fact all DMU suburban trailers, though basically very similar, had slightly different bulkhead window positions between each class.

While built with round buffers, some did receive oval ones later on. The units were never gangway fitted and were not included in the refurbishment programme.