I don't think the systems are connected. If you are still losing coolant fluid, you'll need to find source of leak. Did you ever test the coolant density before and after a noticeable leak to determine if it was water or coolant that you were losing?

 

oh ya, forgot to ask; what has dealership said?

 

Well problem solved. Thanks to Audi Swindon and nit to Audi Newbury. 11 months ago I had to have a new EGR pump fitted by Audi Newbury. This as it turns out was done incorrectly and required a whole new set of seals to fix the leak. Why the pressure test didn't show this leak I don't know but thankfully it was all covered under the 12 months parts and fitting warranty on the pump. Well done Audi Swindon!