The brake fluid is what we call in the USA "DOT 4" (may be called the same in the UK - dunno). It's basically synthetic brake fluid. Any DOT 4 brake fluid is OK, I stick with Pentosin from Germany. I have used Castrol as well in the past with no issue.
Here in the USA, our choices for oil for your car are: Mobil 1 0W40, Castrol Syntec Euro 0W30 "German Castrol", or the BMW oil from the dealer. From my research, I believe the first 2 oils may be better than the BMW stuff.
Yes there are other choices, but those 3 are easily available, at least here.
Coolant: get the BMW stuff.