The e-code head lights are the European headlight standard vs. in the US we have DOT (department of transportation). The e-code headlights have a sharp cut off and puts more light on the road and less in the trees, road signs and other drivers eye. If you have driven a newer production car the headlight pattern is similar to e-code. Not sure when they made the switch in the US. The cool thing about the high performance DOT and e-code headlights is the ability to install high performance H4 bulbs. Standard H4 bulb wattages are available at any automotive parts store. I would strongly recommend upgrading your headlight harness and add headlight relays to avoid overheating your wiring and switches. The stock MG wiring to the headlights is very thin. I purchased a headlight harness with relays form Victoria British

I am running the Autopal H6024 headlights with white 100/55W bulbs, which made nice improvement. Hella and Cibie are other popular high performance brands.

Here are some useful links

 

Below are pictures comparing the e-code vs the standard headlight.  The rounded headlight is standard