@Littleblackflash did you ever find the time to pursue this a bit further? It’s getting cold again and I realise I haven’t pulled my finger outThe parts on the seats are the simple bit. It's just a heater element and sometimes a NTC heat contoller. I wouldn't be supprised if the connector to the relay module to the seat has the same pins, but a different connector housing. It could be a simple re-pinning job.
I'll take a look sometime over the weekend. It may inspire me to start mine.