Your welcome Railer,
Yes your right about the HEP sockets,I think it was more to do with sockets getting damaged that the modification was done afterwards,
The HEP was beyond repair on 209 and 234 and just didn't work well on other locos e.g 219,220 224 226,
Its more of driver comfort that the No1 end is leading on Belfast and Cork services,the fact that its a bigger cab,it seems that it is better insulated.