SUB's were still in service when I went through the South-Western Divisions Training School at Eastleigh, so I've attached the coupling diagram for EMU groups A (4SUB), D (2/4EPB) and E (4VEP, 4CIG). SUB's didn't have different ends, the connectors at each end were idential. However, after the mechanical and air couplings were made, the remaining three - Power, Control and Lighting HAD to be made in that order. I forget why but possibly because everything was derived from the traction current? REP's were slightly different owing to the ETH supply so had separate instructions, as were SE loco hauled trains (especially different sub classes of Cromptons cl33). Before you ask, yes, it was distributed on pink foolscap paper, which is why the image is cropped using an A4 scanner. The annotations are mine