All four tyres were replaced 5000 miles ago to hankook, found out last week the rear tyres are down to 2.5mm on the inside, is this likely an alignment issue?

Also considering changing tyres to michelin all seasons and wondered if anyone is running them?

Hello Steven,

As you probably know, even tyre tread and wear is a must on the Quattro system. Yes, this does sound like an alignment/ suspension issue and needs to be checked. If it were mine, I simply wouldn’t be getting the rear wheel alignment altered without first confirming all suspension components are free from wear. Modern equipment can often be more sophisticated than the operators! , and I only use one local tyre retailer - one where you can actually talk with the operators. 

Hankook tyres? My limited ( non Audi) experience with them has shown they wear quickly. This could just be my non-typical experience, but I would not buy them again, despite the likes of Mercedes fitting them to new vehicles. 
Michelin? With one exception, our just under 170K A3 has run on Michelins throughout its life, and I’ve found that they give a good mileage/£. Yes, of course you can buy cheaper, but you can end up buying more often. That’s not to say that other brands not yet tried will be just as good. 
Michelin Cross Climate? Our non-Audi came with a matching set of these a year ago, and they seem fine, but we haven’t covered that much mileage to judge their rate of wear. 
Hope some of this might help Steven.

Kind regards,

Gareth.