another hint that may help others - I have done approx 127,000 miles and have obviuosly gone thro a lot of tyres and changed a few wheel bearings

On one occasion many miles ago the rear started droning again, and I had only changed the rrear wheel bearings 10,000 miles previous ( again stick to original parts had issues with pattern part bearings - only lasted 20,000 miles) on examining the back i noticed the tyres were stepping

This stepping is a common fault with cheaper tyres and block pattern design, I moved these tyres off the back and put them on the front no more droning noise on the back - on the front now!

So all I have done over the mileage I do is swap the tyres back to front every 60000 miles (the droning to the front soon dissapates as the tyres wear quicker on the front )