Your wiring more or less follows the diagrams I posted in post #2 above except some of the colours in your car are different.
Referring to the wiring diagrams, the black/blue connectors are D71 for the passenger side and D70 for the driver side. The numbers printed in boxes next to D71 and D70 are the pin numbers in the connectors.
The letters printed next to the wires in the diagrams are Italian initial letters for the colours of the wires as follows:
A = Light Blue
B = White
C = Orange
G = Yellow
H = Grey
L = Dark Blue
M = Brown
N = Black
R = Red
S = Pink
V = Green
S = Pink
Wires with a main colour and a tracer colour are shown as e.g. RN (Red/Black), RG (Red/Yellow), BS (White/Pink), NS (Black/Pink), NB (Black/White) etc. Convention is to write the main colour first and the tracer colour second but Italian wiring diagrams don't always follow convention.
The seat motors get power from fuses F56 and F60, both 30 Amp green fuses in the rear fuse box (B45).
The seat heaters get power from fuses F57 and F67, both 10 Amp red fuses in the rear fuse box (B45).
All 4 fuses are supplied by the large black 50 Amp relay in the rear fuse box.
The wires from your passenger side black/blue connector (D71) go to:
Pin 1 (White/Pink) CAN line.*
Pin 2 (Grey) to the rear fuse box (B45) pin 6 and connects to fuse F67.
Pin 3 (Red/Black) to B45 pin 10 and connects to fuse F60.
Pin 4 (Black) to the passenger side earth connection (C20)
Pin 5 (Black/Pink) CAN line.*
Pin 6 (Black) to earth connection C20
The wires from your driver side black/blue connector (D70) go to:
Pin 1 (White/Pink) CAN line.*
Pin 2 (Black/White) to the rear fuse box (B45) pin 7 and connects to fuse F57.
Pin 3 (Red/Yellow) to B45 pin 12 and connects to fuse F56.
Pin 4 (Black) to passenger side earth connection (C20)
Pin 5 (Black/Pink) CAN line. *
Pin 6 (Black) to driver side facia earth connection (C15)
The four power supply wires (Grey, Red/Black, Black/White and Red/Yellow) will be the wires with the same colours that you posted at the rear fuse box. (you posted Black/Grey, it will probably be Black/White) You will probably need to swap the complete rear fuse box from your donor car.
If it isn't already there, you will also need a thick red wire capable of carrying at least 50 Amps to supply pin 1 of the rear fuse box from the engine fuse box (B2). From your photo, it looks as though there is a thick red wire.
You could connect all 4 of the black earth wires to any convenient earth point if it's easier than running them to earth connections C15 and C20.
* The wiring diagram doesn't show where the 4 CAN lines are connected. You may not need to connect them at all, but if you do, they can be connected to the same colour CAN lines anywhere in the car.