Front wheel drive cars with independent rear suspension, especially those with larger wheels, can suffer from uneven rear tyre wear. Lots of us have suffered it. It's generally down to too much rear toe in. It only needs to be out by a fraction of a degree to cause issues.
My car is totally standard and has had it's alignment set up at VW and now drives like a completely different car, with no tyre wear issues at all. They are very sensitive to the slightest changes in geometry. Lowering and modest spacers will need the suspension geometry setting up accordingly, so budget at least another £100 if you want to do the job properly.