I'm quite sure the newer vag diesel lumps by-pass the heater matrix / aircon if there is no load put on the engine to enable them (the engines) to warm up with the little heat these thermally efficient engines produce.
I could be wrong but I think that if you left our car running at tickover all day on the drive, it would not warm up the matrix more than a whisker.
The best thing to do is get in, put a fleece on and drive it hitting 2.5k through all (or as many as possible) gears until the water temp gets to the one quater position, then you can rev it as much as you like.
If you're sitting in trafic freezing your t1ts off, rev and hold it at 2k in between moves, for short periods.
Dont set the heater to manual - I'm sure it will make little diference anyway as the bypass thing will limit the heat to the heater until sufficient is built up in the engine.
Put it on say 25c on auto without aircon and try and keep hitting 2.5k