Seat Heating - retrofit

[trapdoor]

Have been looking into retrofitting seat heating into my 2004 X3. Am somewhat confused as the ETK retroifit info shows a retrofit kit, with a note that the Switch Unit and Seat Covers to be ordered seperately.

Now, I know I will need a new Switch Unit, which has the seat switches, however the ETK does not show any different seat covers which have heating elements installed.

So, the question is, do the X3 Sports seats come with the heating already installed, and all that is required is a replacement Switch Unit and possibly a fuse (or whatever is in the retrofit kit)?

Has anyone done the retrofit and know what is involved?

Thanks.