The BMW Part No. is 07 12 9 905 537 & they cost £2.33 each x 12 = £27.96.

A trip to Hawk Fasteners in Middlesbrough came up with some Stainless Steel M6 x 30 Socket Head Cap Screws & Washers (12 off) for £6.21.
If you have changed any screws or fixings etc. for Stainless Steel, where did you get them from, thanks.