While Goran is helping with gathering statistics of how genuine Audi clock antenna behaves in the UK in genuine location in a car with heated windscreen I'm continuing my research.
I have found out that on many audi models clock receiver is mounted in rear bumper area.
Next step: because I have ski hatch in my car I'm going to extend receiver wires buy ~3 meters and snake them temporarily to boot area via the ski hatch. I'm going to try to find good reception area. The first place I'm going to try is under rear parcel shelf. There is good access there via boot. We have 4 circular holes in the aluminium chassis between boot area and parcel shelf. I'm going to stick receiver under parcel shelf through those holes in the boot and there is just enough space for the receiver.
In parallel I'm going to order monster DCF antenna from Germany.