Electric seats

[IMAY2023]

Looking to replace textile seats for some leather ones. Today the seats are heated and manual. It’s quite hard to find manual leather seats. Are electric seats plug n play?  Is it any problem to program these to the car at the dealer? Car is an XC40.

No it's not plug and play in your case.  Since your current seats are manual, most likely either you do not have the seat controller at all or bunch of missing wiring.  
If you purchase used seats make sure the airbag is not blown and have the controller under the seat. Then you 'll need to wire the missing ones (depending on the features of the used seat)  then you will need to enable those features from the orbit.

Is there anywhere wiring diagrams available for these cars? Earlier models were widely available on internet. I’m thinking electric seats without memory might could be working since I got the heating? There’s a module under the seat, at least for the heating.

The wiring diagrams https://forums.spaycetech.com/showthread.php?tid=455 
Let's clarfy some points. 
The heated seats have their own LIN module under the seats, connected to the CCM.   When you press on the heated seats on screen, Center display sends LIN command to IHU and IHU sends turn on heated seats command to CEM via Flexray bus then CEM sends command to CCM via CAN BUS and finally CCM sends LIN command to the module under the seats.  It has nothing to do with Seat module nor the memory seats. 

Electrick and memory seats are different.  Not all electric seats have memory option.  The motors are different between with and without memory seats. Memory ones have position sensors inside the motors. (4 wires on each motor) connected to the Seat module. 
Memory button on the door is connected to the door module in LIN, and the Door module is connected to the seat module in CAN bus.  The memory positions are stored in the seat module.