W124 2.6 Memory Seats???
 

I have done a search on the above but haven't quite come up with anything. General question, on W124 2.6 300e with power non-memory seats ? Is it just a matter of changing the switch to one with memory option for the seat to become a memory seat?

No, you'll need to run quite a bit of wire from the seat switch down to the seat and buy a power seat control unit with the memory feature, at the very least.

I was considering this retrofit for my 1993 300E2.8 - I can understand the changing of the power seat controls in the door, but why run cabling down to the seat itself - What's the extra cable for?

I'm guessing that the seat switch does not have the acutal seat-position "memory"; the settings are stored either in the control unit, or in a third (separate) unit designed for the memory function.