John, there's a place in Crumlin doing these retrofits everyday.
I don't know if they can wire to the OEM buttons or not, but maybe worth a call.

My cousin is getting a sunroof fitted and while I was dropping him there, they had a line of brand new cars all getting one or more of the following retro fitted, sunroof on a brand new A6, heated leather in a new Toyota Rav 4 and sunroof to 3x i40's.

They said they do it all the time. They are well aware of cartronics, and maintain that they used to supply cartronics (Gerry) while they were in operation here.

It's the autoglaze place in the little industrial estate on the left hand side just as you cross over the canal heading out of town into Crumlin.