The GE outer suburban EMUs (classes 305, 307* & 308) all had 6-a-side non-corridor compartments in the motor cars from new - c.1960 untile they were either modified or scrapped.The EPB's had them as well at the start.
* The pantograph and brake area on the original 1500VDC trains (before they were classified as class 307s) was moved to a DTS (making it a DTBS - so there were two fully 6-a-side cars leaving 18 x 12-seat compartments).