Many thanks for that, sounds like it will be expensive.Apart from going through the dealer for a new seat pad, this company fit Mercedes heated seat pads.
https://www.dkschweizer.co.uk/heated-seats
If you are closer to the M3, Comand online in Lightwater may be able to assist .
https://www.commandonline.co.uk/
Thanks for the info, yes it is part of the seat but I believe one can retro fit a compatible heat pad just can’t find one.Are the heater elements not part of the seat covering? They often are, which makes it a dear do to replace