A number of suppliers in the UK mate. Try Tim at Cleanyourcar.co.uk
Best to drop him a mail or give him a call and he will advise you on what products to get.
He stocks both the standard Menzerna range of polishes (Powergloss, Intensive Polish, Final Finish Polish) and the new Professional range of Menzerna polishes (Intensive Polish 3.01 and Final Finish).
The new professional range are designed for ceramiclear paints as found on the new Mercedes Benz range and others (Rolls Royce). These paints are very hard, they are sometimes termed "scratch resistant paints".
The pro polishes have much harder, but smaller abrassives and it has been found that these work better on harder paint such as that found on Audi's.
I've not had a chance to try out my Professional polishes yet.
One thing I am also told is that the Professional polishes dust alot less than the standard polishes, you'll also find the standard polishes dry very quickly. Too quickly to effectively work on Audi's.
I can heartily recommend you visit detailingworld and have a look in the guides section, particularly the slow cut method and Menzerna polishes. This method allows you to work the standard polishes alot longer (by using some Quik Detailer as a lube), this does work well and I have had success with this on my Audi using Powergloss.