Having been advised by my stealer that my rear brake pads needed changing and that they wanted £265 for the job (rears only), although there were no warning lights showing, I checked both front and rear pads visually through the wheels and could see that the fronts were about 5-6mm and the rears about 4-5mm.
Checked on the forum where there are several excellent write-ups and also on Google and as a retired mechanic I could see no issues in doing the change myself.
Purchased both front and rear sets of Pagid brake pads for about £72 and did both jobs yesterday in about 5 hours without any issues whatever. Just a note of warning, the sensors have a very small "U" shaped metal clip which falls off when you remove it from the brake pad and is easily missed when you do the first one
!!. This clip ensures a tight fit between sensor and brake pad.
My X3 F25 has 23500 mls on the clock so I thought that changing pads was a bit premature. All discs were absolutely fine, no scoring or ridging.
The remaining pad thicknesses were: Front 6mm and Rears 4mm so actually I need not have changed the fronts yet but anyway job is now done. Incidentally thickness of new pads is Front 19mm and rears 18mm.
I will now need to reset the mileages in the iDrive system.
It seems to me that the sensors are not touched until the brake pad thickness gets to around 2-3mm as neither of my sensors had been touched.
Just saved myself about £450
.