Just to bump this thread. I am very keen about checking my tyres, always look at the treads and check the pressures every month. Recently my car was in the garage for some brake work, whilst it was on the ramp I had a chance to check the tyres properly, I was shocked to see that the rear tyres had worn down to the canvas on the very inside edge, this is not visible when the car is on the floor.
After checking on the internet it would appear that this is very common with BM's running wide tyres. If you are running wide tyres please get down on the floor, or better still, get the car on a ramp and carefully check your tyres, you may be shocked at what you find.
My tyre:-