Where/who is your go to for parts? Some obviously come from specialist retailers, others from BMW. But does anyone use a particular company because of service and/or supplies?
Autodoc, if they have stock. They are not the quickest at delivering as all parts come from Zee Germans but their prices and choice are better than anyone overall IME.
For BMW dealer parts; Group1 in Lincoln and I believe Cotswold BMW will give a decent forum discount (Group1 give around 10%). Group1 Lincoln were Sopers until recently.