Thanks for all your replies Guys.
After trying to work out exactly what had to be done to just adjust pad thickness, I found the Ross-tech Wiki had too little detail. Somewhere else on the web had a more precise process which was basically:
1) Adjust the pad thickness [as per Ross Tech]
2) Then run the Function test [not sure that's explained on Ross Tech clearly]. Not forgetting the 'wait 30 secs' after function text completes.
3) Clear the DTCs
This gave me confidence to have a go; however, that didn't work even after 4 attempts! [there's a Ross -tech Video saying you might have to do it several times, but I'm not sure why it would work on a 4th attempt if it didn't work on the first three
]. After that, I still had the same fault codes and the 'yellow' brake alarm in the DIS.
As a result decided I needed to spend some money and got my local [non Audi] Audi specialist to put new pads in anyway. No faults now but they would have done the proper Open Caliper, replace Pads, Close Caliper, Thickness Adjust, Function test, etc.
As an aside I asked for the old pads; the outer pads [the ones I could see] were 5mm - the inner ones were 2-3mm. And I see from the instructions that pad replacement should be done at 3mm, so they were due anyway.
Julian