Irregular braking effect is more usually caused by deposited pad material from improper braking/bedding technique. Don***8217;t fix what ain***8217;t broke lest one fix until broke.

If they are using BMW parts for discs and pads then that is very cheap!!! If you are using after market parts well you pay your money and take your chance. The 640 is a powerful and heavy car so stopping capability is very important. I for my own part will always use BMW original parts at least for the discs, as BMW are possibly one of the few manufactures that balance the discs in manufacture. In the UK we do not have the range of top end disc and brake pad suppliers that have in the States for example. Even then many will stick with BMW disc's but use different pads due to volume of dust generated by BMW original pads.
Dont forget to replace the wear pad sensors thinking to save money and don't go after market as they can cause error codes!!!

Update

Hi folks - thanks for the posts.
I decided to go ahead. They are Brembo discs and pads. Only needed to change the front in the end at £360 so will see how I go. Was advised rear discs are probably needing change soon but its driving fine for now and brakes felt great on the way home. Only changed front and rear pads in January so at least I will get some additional wear from the rears and can budget for the change!