To my delight, I found myself original MB 2nd row, rear heated seat covers. The 2nd row seats on my vehicle were non heated. The covers I bought all came with heater cables, not my choice but so glad to have them.
The vehicle came with heated front seats and that's been great for us but not for the rear passengers.
I figured it could be a straight forward thing, add the cables from the seats to the rear control unit located under the seat and from there to the switch cluster and voila. Not so.

The problem is, I am restricted by lack of wiring cables, I have no access to the part nos.

I use 'MBTeile' for online part search and it is good to a certain point, but not in this case, there isn't enough details on the seat diagram to show the wiring cables.
The diagram shows all the cables as straight lines and below that is a cluster of part nos. I cannot tell which is which. Normally, you see more part detail on dealer websites.
I can only assume with some surety that I lack reading skills for part nos.

Does anyone know of a more detailed parts search or where should one go for such a search. Many times I have been stuck for the lack of part details.

I bought a switch cluster from ebay, it is the same as the one on the car, except it has as extra seat heater switches in addition to the air-condition etc, its a one up from what already on there. I only have to find out if I need new control unit under the rear seats for the cabling.

Perhaps someone could lift up the rear seats and get me those part nos.

I would really appreciate some guidance on this, I will be always in your debt. Thank you