2005 a3 3.2 emissions light problem

Hey guys this is my first post so apologies for any noobness.

The emissions light on my a3 has come on. I've had this problem before about 5-6 months ago and it was 'sorted' back at the dealers. But now it's reared it's ugly head and come back to haunt me.

Its being very stubborn this time however, it's been 'fixed' and come back on twice. The first time the lambda probe was changed and the second time some settings on the ecu were reset and they ran the car for a night, but it still came back on when i went to collect it.

The dealers rang me yesterday saying that both lambda probes have been changed, apparently there are 2? I managed to have a look at the paper work the second time i went to collect the car and from what i could make out i think the fault codes were P2626 or P2629 which apparently points to the lambda probes being faulty?

Anyway, is there anything else i can do or maybe suggest to the garage? The car still has 1 year warranty and i don't want to be paying out the nose to fix this problem later on. Of course i don't want to seem like a complete arse trying to tell them how to do their job.

thx!