Hi DM
I hope i can be of help here as i did exactly what you want to do earlier this year - only with Dura Ace
I asked PBK that exact same question - what happens with warranty?? their reply was that it was NOT an international warranty that came with the group, and if you had a problem with components inside the warranty period, to send the offending item back & they would determine if it were a warranty issue & replace/fix accordingly.
So short answer - your in for a lot of hassles if things do go wrong (especially if you have to pay someone to remove the bottom bracket/RD/FD/sti lever), but it is covered under warranty in UK. But please check with them - dont take my word for it, conditions change.
All in all, i bought the Groupset, had a friend (bike mechanic) help/teach me to install it, all went well & have now clocked 1300kms with only the usual cable adjustments needed so far🙂
OH and saved about AUD600 in the process😄
To answer your question on LBS fixing faulty gear - well i am sure they would, i just dont think it would be under warranty and would probably charge accordingly.