I've seen some companies that fit 3rd party but I'm looking for one that will fit OEM with full hookup to the dashboard switches and entertainment unit.

 

East Coast Retrofits used to do it but it's not on their menu anymore.

@East_Yorkshire_Retrofits   Any use?

 

Sorry that's who I meant, they used to do heated seats but not anymore

They still offer it for some cars. It's probably worth contacting them directly as it's certainly within their skill set.

Drop Andy (Young) a message - Yorkshire VWAG definetly do it. 

 

https://www.yorkshirevwagretrofits.co.uk/products/untitled-mar3_11-47 

 

They can either adapt your current seats, or supply entirely new ones.